Popular Science Monthly/Volume 75/November 1909/Desert Scenes in Zacatecas
|DESERT SCENES IN ZACATECAS|
By Professor J. E. KIRKWOOD
UNIVERSITY OF MONTANA
ABOUT 400,000 square miles of desert lie south and west of the Rio Grande. Much of this vast area occupies the great tableland, bounded east and west by long mountain ranges and reaching southward several hundred miles, where it becomes broken by more fertile areas; all this being, in fact, a continuation of the great southwestern desert region of the United States which prevails from Texas to California. The aspects of its southern extension vary with local conditions within certain limits, and with its lowering latitude new elements enter into its composition, but on the other hand many of the features characteristic of a Texas or an Arizona landscape are conspicuous in its geological formations, its fauna and its flora. This region has, however, certain significant peculiarities which give the central Mexican plateau a character of its own.
Typically representative of the conditions on much of this great plateau is the northern part of the state of Zacatecas. Traversed by fragmentary mountain ranges with a general trend from northwest to southeast, only in a few places do its plains stretch level to the horizon. On every hand the skyline is formed by the heaving back of some ridge or group of mountains whose summits rise from 1,000 to 4,000 feet above the plain. The plain itself is 6,000 feet elevation, more or less, and the mountains appear as if almost submerged in it. Here and there are lower ranges whose heads are scarcely lifted above the plain and whose softly rounded outlines show that leveling forces have long been at work upon them, or that their softer materials have more readily yielded to eroding forces. Other peaks rise higher and a few of these are rugged and sharp with steep declivities, but for the most part the evenly rounded outline prevails.
The more or less isolated ranges, the Sierras of the Potrero, the Zuloaga, Zapoca, Guadaloupe, Oratorio, Ramirez, Chivo, Caballos, etc., are all on an area some sixty by seventy miles in extent, which constitutes the Hacienda de Cedros, a corner of which the Mexican Central Railroad crosses southeast of Torreon between Rivas and Carlos. This Hacienda, which lies mostly to the east of the sun-baked village of Camacho, extends also to the west fully twenty miles. An interesting estate and sufficiently large from an American standpoint it is, but one of many of its kind in Mexico, managed in a feudal way. It is to this particular region that the accompanying discussion pertains.
Looking westward, far across the broad Camacho plain, standing
Map of the Hacienda de Cedros, a private estate of over two million acres, on which dwell some two thousand people.
well up on the horizon are the high Mesas del Zorillo. Their broad level tops lie in the same plane, at their borders a sheer descent is visible to the point where the talus slope begins and slants off in graceful lines to the rolling lands below. But such configurations are rare in that region. Here and there what is left of that stratum which forms the high floor of these Mesas may be visible, but only as vestiges, for they have mostly disappeared.
Standing at the edge of one of these wide plains and looking across, one may survey at a glance twenty to forty miles of mountain barrier along the opposite side, thirty to fifty miles away. Deep scalloped with cañons and ravines which divide and subdivide into successively smaller branches as we follow their course upwards, they are ultimately lost in the rounded brow of the mountain. Below the steeper slopes the low-lying, far-outreaching butresses of the range finally sink into the plain. At the mouths of the cañons, broad fans of silt, gravel and other detritus from the heights above, spread out and meet their neighbors on the right and left until a long, slightly undulating footslope is formed, and gradually merge into the floor of the valley. Thus the wide valley is gradually being made wider by the building up of its floor, which is the accumulation of ages of the wash from the mountains; the nature of the process is obvious. Where a deep arroyo cuts down through the land a section of the deposit shows in places stratification of clay, sand and gravel. Here and there a well is bored and the same story is told. Every valley between these mountain ranges presents the same features, a gentle slope for miles from either side, so gentle that in walking over it one hardly realizes that it is not level, and in the center is—not a stream—but a shallow basin, frequently lined with salty incrustation. Such is the character of the Bolsón, as it is called, which is also a marked feature in the physiography of southern Arizona.
Into these basins the arroyos pour the floods from the mountains. One finds the arroyo in the higher parts of the plain nearer the mountain where the steeper incline gives more velocity and erosive force to the stream. Lateral valleys which lie between high slopes usually develop the arroyo to a marked degree. The deep basin between the ridges, filled with the detrital wash from the slopes, is readily eroded by the swift streams which are produced frequently by the torrential rains of these regions. Running lengthwise through the midst of an apparently level valley floor, these arroyos are often invisible a few feet away, and the traveler may be entirely unconscious of the presence of a ditch thirty feet deep and possibly fifty wide, with perpendicular walls, hardly fifty paces away. The walls of these arroyos are being constantly undermined, and the materials, caving into the channel, are carried out with the rest of the wash; at the same time the head of the arroyo is receding toward the higher land and the channel becomes more and more shallow as the underlying rock comes nearer the surface. As the arroyo extends out into the plain its fall becomes less, the power of erosion by the water decreases and the channel is finally lost on the lower slope.
Thus the composition of the mountains is responsible for the composition of the valley floor. Limestone is the predominating material. Rocks of igneous origin are less conspicuous, but are present, and mineral-bearing veins are plentiful. Occasionally heavy formations of calcareous tufa may be found where springs issue from the hills, as-at the village of Cedros, situated at the end of a short range. In deep and sheltered ditches salts collect on the clay and hang in slender glistening crystals to its surface. The ooze of calcium solutions is everywhere visible in the formation of caliche, which forms a hard, impervious and impenetrable layer on or near the surface of the ground. Here and there it cements together stones and gravel in a solid mass, resistant to weathering and erosion.
But few springs are found and these usually at the foot of the higher slopes. At the western end of a small range, the Sierra del Potrero. water comes to the surface in numbers of strong springs, and on this oasis is built the village of Cedros, the administrative seat of the Hacienda of the Cedars. From the limestone rock, cropping out on the toe of the range, the springs issue forth. One at least of these is warm.
the others cold; some feed a small rivulet, across which one might step with ease, that passes through a series of reservoirs and is used in irrigating the gardens, some supply the baths, and others the troughs where the cattle come to drink.
But this wealth of water, for wealth it is in such a country, is not general. One would go far to find so splendid a supply as feeds the industries of this place. Here and there wells are sunk in the valleys and water is found at a depth of forty feet more or less, but often drilling goes much deeper without finding any.
The sites of these springs are here, as everywhere else in deserts, oases of fertility, visible sometimes a day's journey across the broad valleys, and marked in the broad expanse of desert landscape by dark tops of huge cottonwoods, and the light reflected from the whitewashed walls of adobe houses. The number and quality of the springs determine the size of the hamlet and sometimes the nature of its operations. Upon arrival we may find also ash and pepper trees, pecans, avocadoes, figs, pomegranates, apples and grapes, rows of magueys and hedges of tuna-bearing nopáls. Onions, garlics and chilis are the principal garden crops, and flowers (poppies, asters, roses, etc.) in pots or beds in the patios or dooryards of nearly all dwellings, however humble. Fields of corn and barley, with calabasas (squashes), are scattered about the plain not far away, where crops are matured in the short season of the summer rains. Their corn planted in July is harvested in October, its growth hastened by irrigation of a primitive sort; running a ditch along the face of the slope, the ranchero collects the run-off from the rains and directs it on to his field. On some of these fields corn grows to the height of ten feet with a degree of luxuriance that would gladden the heart of a northern farmer.
Although no permanent streams of any consequence exist, yet the rapid drainage of the land makes feasible a mode of existence otherwise impossible. The herdsman pushes out away from walls and springs and establishes himself in the midst of the desert. Choosing a place where the land lies to form a basin or wide valley, he throws a dam across the mouth and collects the run-off from a large area. For this purpose a gently sloping drainage basin is preferred, else the labor of building the dam will come to naught in a few years by the reservoir's becoming filled with silt and drift; moreover, the rushing torrent may cut through the embankment and drain the tank dry. I have seen old tanks which had been filled to a depth of fifteen feet or more, and as the earthen dam was finally cut through, the later floods had sluiced down an arroyo through the flat sedimentary plain above. So the tanks in such situations are short lived, but where fed by the gentle drainage of a gravelly plain they may last indefinitely and supply water the year round to large herds. Frequently these tanks hold water covering several acres at the height of the dry season, and when at its deepest it may assume the proportions of a small lake. Some of the dams are strong and well-built structures of stone masonry a half mile or more in length and ten to twenty feet in height. To the "tanques" come the horses, the mules, the burros, the sheep, the goats and every other animal of the desert; they drink the turbid liquid, they wade in it, they bathe in it, they discharge into it, and all around the margin is a fringe of greenish drift and scum, but it is water in a thirsty land and man is grateful for it. It is the objective camping point in the day's travels and at noonday the cool shade on its banks is the favorite resting-place for man and beast.
From one to two and a half feet of rain falls on this land in a year, depending partly on the altitude and local conditions. Records of rainfall at Chihuahua and San Luis Potosi show 10.86 and 10.41 inches, respectively, for one year (1901), and at the city of Zacatecas the average for ten years (1897-1907) was thirty-one and a half inches. The precipitation at Cedros for one year (1907-8) was about eighteen inches.
Palma china (Yucca australis) in the Village of Cedros. Photo by B. A. Crane.
The heavy rains, sometimes as much as an inch in a few hours, run off with great rapidity through the drainage channels and twenty-four hours later the sides of the mountains and the footslopes appear as if not having known a rain in six months. Here and there in the bottoms of the cañons a pocket in the rock holds a gallon or two of sweet pure water, and out upon the plain pools may linger for a few days on the clay.
Here the summer months are the months of rain, but in most months of the year a little rain may be had. As springtime advances clouds may be seen along the distant slopes and among the peaks with a trailing haze of rain beneath. Though in the summer-time the rain clouds are partial to the highlands, yet more often do they wander out across the plain. Scarce a day of summer passes but showers may be seen falling on some part of the landscape, but the amount falling on any particular area is relatively small.
The isolation of these places is intense. The light of midday dazzles the eyes as it is reflected from the walls of the houses, the dust of the road, or the whitish soil of hill or valley. Heat is a liberal accompaniment of the fierce glare of light, as blistered lips may abundantly testify after a few hours riding across the desert. The Mexican knows the value of his broad-brimmed sombrero and is seldom to be found without it, if indeed we may induce him to leave the shade of the tree or the dark interior of his adobe dwelling at the middle of the day. But the shade, even the thin shade of the mesquite, is a place of comfort, affording some shelter from the direct rays of the sun. Even alongside a thermometer registering over 100° in the shade, no discomfort may be felt in the thin and relatively dry air of this climate.
The most suggestive feature of the desert is its vegetation and the variety of the plants which it supports. The great number of species which by some peculiar fitness of their own are able to maintain themselves in the midst of seemingly impossible conditions, must certainly impress one accustomed to the abundant vegetation of the green fields and woodlands of the better-watered sections of the country, though the number of individuals of a race may be considerably less. This is not true of all species, but the fact is quite patent to any one who has seen even a little of desert vegetation, having in mind the almost impenetrable vegetation of some of our northern woodlands. Across the desert of Zacatecas one may ride in any direction, limited only by the perpendicular banks of arroyos, or mountain barriers. The floor of the desert here also is bare and clean for the most part, which means a paucity of herbaceous plants. Such herbaceous forms as do exist are found usually in shaded situations, under the shelter of woody perennials.
The vegetation of this region as it appears to one at a casual glance seems to be composed of Yuccas, shrubs and small trees, Agaves and cacti and these constitute the predominant features of the plant life in varied arrangements and conditions.
The most conspicuous element in this vegetation is the palma, so called, which may be seen on every hand. Two kinds are usually met with; one a straight-stemmed plant, six to ten feet in height, with a crown of stiff radiating sword-like leaves, much prized for the fiber or ixtli which it yields. This plant, Samuela carnerosana, which the native calls palma zamandoca, grows in great abundance on the higher lands, from the upper footslopes a thousand feet up the mountainside. On the high rolling land south of Saltillo, from Carneros to Fraile and beyond, thousands of acres are covered with this splendid plant. In March and April they are in full bloom and one may go far to find a more pleasing picture than these tall plants with their erect panicles of creamy-white flowers, two or three feet in height. This plant grows so
slowly that the increment of one season can not be marked without precise measurements, but year by year the lower leaves of the foliage crown die and add to the thatch of dry leaves that cover the trunk below. The trunk itself is six inches to a foot in diameter, a mass of spongy tissue with a more dense outer rind. Of these stems the peon makes fences, or sets them palisade-like for the walls of his hut, or hollows them out for bee-hives. The leaves of the plant make the most convenient thatch for his hut, and from the fibers of its leaves he makes ropes and sundry other articles of convenience. Palma china, as the native calls it, known to botany as Yucca australis, is a close relative of the preceding and often occurs in the same situations. Usually, however, this plant does not ascend to the heights attained by its neighbor, but is a native of the wide valley lands, where it often occurs in great profusion as at Pal mas Grandes, a few miles west of Mazapil, and again on the footslopes some twenty miles east of Camacho. This Yucca is the most striking of all the plants seen on this desert. Beaching a height of 35 to 40 feet, and having a trunk diameter of two to three feet, its upper portion is divided into straggling branches clothed for a foot or two from the tip with rigid outstanding leaves a foot and a half long. The branching of palma china is never symmetrical, but usually both trunk and branches are contorted and arched in various directions. Occasionally one is found straight and tall and beautiful, such as grew by a peon's hut in the village of Cedros, and one which was found on the plain near Symón was as grand a tree as an oak of two centuries and probably not much younger. This magnificent palma must have been close to forty feet in height, with a hundred branches which filled out the hemispherical top with symmetry and beauty. The trunk of this palma was near three feet in diameter four feet from the ground, and its thickened base below was not far from six feet across. The flower cluster of this plant is about three feet long and the creamy flowers which abound in June are much prized by the people as food. This plant also yields fiber, which, however, is not so generally used as that of its neighbor, owing doubtless to the abundance of the latter, which has longer and more accessible leaves. Some of the other desert plants less conspicuous than the Yuccas are hardly less interesting. In numbers the Maguey and its family outrank almost everything else. From Agave americana down to A. lechuguilla and Hechtia they are everywhere abundant. While the huge pulque maguey is found in this region at least only in cultivation, its lesser relatives are on a thousand hills, sometimes leaving little room for anything else to grow. Three species of Agave are abundant. Two of these, A. lechuguilla and A. falcata, are never found on the level plain, but as soon as one begins the ascent of the low ridges which rise but little above the valley he is almost sure to encounter A. lechtiguilla. We may say encounter advisedly, for their leaves are as so many daggers set at all angles to impale the unwary. The rigid leaves about a foot long are armed with terminal spines as sharp as needles and as strong as nails. These in places, especially on the low limestone ridges, are so numerous that one with difficulty can make his way through. In June this plant is at the height of its flowering season and over large areas the flowering shoots, ten to twelve feet tall, are everywhere conspicuous. The stems of last year have fallen, and the new ones soon ripen their seed and terminate the life of the plant. The leaves of this plant are especially valuable for fiber and it is one of the most important of native Mexican plants. From it the native also obtains amole, the short stem and leaf bases, which, when crushed, has marked saponaceous properties, and seems to justify the esteem in which it is held, if one may judge by results. A. falcata occupies the slopes of the ridges, but is rare as compared with A. lechuguilla. Its flower stalk is smaller on the whole than that of its neighbor and its flowers much darker colored. Its sickle-shaped leaves are pointed inward and it is, therefore, not nearly so unpleasant to meet as Lechuguilla. But its fiber is little used, probably owing to the scarcity of the plant and the great abundance of the other species which is more easily worked.
Agave asperrima is one of the plants which the traveler first notices in the desert of Zacatecas. Its bluish-green leaves are usually less than three feet in length as it grows in the desert, but are sharply armed
with stout spines both terminal and lateral, which make them formidable objects to meet. These plants spread by stolons and form impenetrable masses where they monopolize the ground. This agave grows in greatest abundance on the plain, where it frequently impedes the progress of a horseman quite effectually. It also spreads upward on the ridges and in the canons to points a thousand feet above the plain. Its flowering season is in June, though it loiters along in this business through the whole summer. The flowering shoot is similar to that of A. americana, but hardly exceeds fifteen feet in height. But these great flowering shoots are of great interest in their strength and beauty, looming up against the sky on the crest of some ridge, and not the least in the fact that this huge inflorescence represents the culminating vital activity of the whole life of the plant. Slowly through the years the materials have been gathering for this particular task, and finally in a few short weeks of summer the supreme work is consummated, and the great candelabrum of branches stands forth with its hundreds of seed capsules, while the erstwhile luxuriant leaves are sere and withered, their substance, as indeed the whole life of the plant, sacrificed to this one supreme effort toward the propagation of its kind. When in bloom the inflorescence is surrounded by myriads of flies and other insects attracted by the abundant nectar which the flowers secrete. These flowers in press, if not killed, continue for days to produce the viscid sweetish fluid which the natives collect and call miél or honey. When the seeds are ripe the pod splits down from above and spreads apart slightly, so that a few seeds are easily shaken out by a gust of wind. The inflorescence, though dead, may stand for a year or more, and the seeds that it bears may be scattered over a wide area.
Before this plant comes into bloom the tender apex of the short stem is often used as food. Out in isolated places among the mountains one may come upon a rude circle of heavy stones bordering a shallow pit. The Mexican would say that here they were preparing quiote by taking the hearts of the magueys and roasting them in the pit. Upon further inquiry he will say that these morsels are covered with earth and stones and the fire built over them and kept for some hours. The older leaves yield a fiber for cordage, though this plant to a less degree than its larger relative, A. americana. Many uses are found for the maguey; in fact hardly any other plant of Mexico serves the people in so many ways as this one. It provides food and drink, it yields fine strong fibers for ropes, fabrics and other articles. It has served in the manufacture of paper and enters into the construction of fences and buildings. It formerly found use in religious rites and was part of the material of weapons.
As ornamental plants the cultivated magueys are hard to beat. During its fifteen years' or more life it produces relatively few leaves, but towards the close of its span of years one hundred or more of these may be in evidence, each somewhat narrow, six to ten feet in length and often weighing as much as one hundred pounds. Most of them are a dull dark green, some are margined with yellow or yellowish green. They are often planted as hedges or borders, and as such they are very attractive to look at. The short stem which in all the years has not attained a height of two feet now suddenly shoots up to thirty feet, its outstanding branches in symmetrical order enhancing its dignity and beauty beyond that of most other plants.
On the slopes of many foothills that rise from the edge of the desert plain and often on the higher slopes in great profusion, one finds a stately plant which is always conspicuous and always beautiful. Something about the sotól makes it especially attractive, with its pale green leaves an inch wide and a yard long, the tips of which often overtop a man's he.ad. But these leaves, though beautiful to look upon, are well armed against any invader by means of many forward set teeth along their margins. In fact, a leaf of Dasylirion is like a piece of doublee-edged band saw.
Under the hot sun of May and June the flower stalk ascends from the center of the crown of leaves and carries its topmost flowers to twice the height of the horseman riding by. These flowers, unlike those of the maguey, are small and borne on a long and slender, though compact panicle; they are monœcious, therefore not all the tall stems
are destined to bear the small triangular fruits that often remain the following winter on the stalk that bore them.
This plant, besides being one of the most attractive of the whole desert flora, is not without its uses, both legitimate and otherwise. From the leaves of sotol the natives weave mats and various other articles of utility. They split the long leaves into narrow strips which they weave into hats. But this plant, like the maguey, also furnishes food and drink. The central cabbage-like bud is cooked and eaten. This central bud, and the thick top of the stem below it, are used much in the manufacture of a fiery liquor called Sotól, of rank intoxicating power.
While the plants above cited are striking and characteristic features of this desert vegetation, yet even more common and more characteristic of deserts in general are the cacti, which abound in species and individuals. Cactus, Echinocactus, Cereus, Echinocereus, Mamillaria and Opuntias of both divisions are everywhere. Down on the open plain the nopals (Platopuntias) abound, as one soon discovers who tries to ride across country. The broad flat joints of these plants are everywhere. Here and there a cluster of bisnaga colorada (Echinocactus pilosus) shows the top of its cylindrical body bristling with red spines above the low bushes, for this bisnaga, as the native calls it, does not grow very tall, five feet being about its maximum. It blooms in June and successions of yellow fruits follow the flowers. These lemon-yellow fruits about the size of a lime are possessed also of the lime's acid properties. But this plant is not content with the lowlands, but climbs to the top of the mountain above, where I saw some of the largest of its kind.
Echinocactus ingens, like nearly all of the cacti of this desert, prefers the hills, and there its thick trunk, bristling with long straight spines, grows to a diameter of a barrel and as much as five feet in height. This bears its flowers in a furrow across the top. The pulp of this plant is said by the peons to be sweet, but one who has* tasted other cacti which they eat, may be content to leave the appraisal of this delicacy to others.
The opuntias which cover the plain and mountain are of abundant interest in their variety and numbers. The cylindropuntias abound in forms of cholla, cardencia and tazajillo, according to native terminology, with spines long and sharp and barbed, which penetrate with ease thick leather leggings, and where they stick they stay. In this the tazajillo, which grows as high as a horse's back, is especially to be dreaded, with its stiff slender spines; it separates its joints at a touch and sends them along with the passer-by. Under and around these plants scores of these joints are busy taking root, though one seldom finds thickets of tazajillo. Few of these young plants really have a future before them, though there are enough of them as it is. But the cardencias, arborescent opuntias like the species mammilata, spinosior, etc., of the Arizona desert, are not so savage as the cholla, nor so unexpectedly met with as their more slender and less conspicuous relatives, the tazajillos, as above described. In its varied forms the nopál, or flat-jointed Opuntia, is of more interest to the native than all the other cactus forms. This is about the only kind of cactus that may serve as fodder for cattle, and it is a common sight to behold some hundreds of pounds of one of these species carried on passing ox-carts. At the last camp where these travelers rested one could probably find the remains of a fire where they had burned off the spines of a number of nopals, which indeed is the principal diet of their oxen.
Some of these nopáls are of imposing size and aspect, but mostly they are low procumbent forms, branching out in all directions, pushing forth segment after segment from the lower forward margin of the laterally compressed joint. Along the upper margin occur the flowers and the succession of fruits in varying shades of yellow and red. Here and there at higher altitudes are forms which produce edible fruits not unlike the edible tunas which are produced under cultivation. It seems quite possible that these may be the forerunners of some of the cultivated varieties, inasmuch as the preponderance of evidence points to Mexican origin for the tuna-bearing nopáls. Again we find on the hills a small and compact species which has little to recommend it. This, Opuntia microdasys, has branches closely set with coarse spicules which are easily detached and are said to be a frequent cause of blindness
among horses and cattle. The animals nosing about among the branches of this plant for some tuft of grass or other morsel, dislodge the glochids and get them in their eyes. Every well-appointed dooryard or garden has one or more species of the cultivated cactus which produces edible fruits of which the Mexican is very fond. These are of many varieties, differing in the characters of the branches and the fruits, the latter varying in color from the deepest red to lemon color and in form entirely distinct. They form a very important item in the short list of foods upon which the poorer classes live.
In this desert region one can not but be impressed with the number and variety of the woody plants, shrubs and small trees, which are to be seen on every hand. Many of these are common in our own southwest—mezquite, ocotillo, creosote bush, Ephedra, Condalia, Koeberlinia, species of Atriplex and Acacia are among the most conspicuous, some are the same species and others different, and the less obvious things are, Lippia, Buddleia, Mortonia and many others. In all these the families of the Leguminosæ, Labiatæ and Compositæ are especially prominent, as they are elsewhere in desert regions. The shrubby growth gives color to the landscape, and in many places its whole aspect and character is due to these plants more than to the yuccas, agaves or cacti. Very few trees in this desert are more than fifteen feet high and the majority of them are much less, so that in no sense does the country seem wooded, except upon the highest ranges where pines and oaks occur.
Among these desert shrubs are some of unusual beauty. There is Cassia wislizeni, quite common, a tall graceful bush with large panicles of orange-colored flowers, a plant which might well be valued by horticulturists of the north. All through July and August these delight the eye and stand out in conspicuous contrast with the surrounding vegetation. Pinacate they call it, though the reason is not obvious. Again if we walk out over the lower slopes not far from the banks of some arroyo we may come upon the beautiful "huisache," Acacia farnesiana, in full bloom if the time is summer. This plant with its small delicate leaves, its white spines, its little balls of yellow flowers scattered in profusion along the younger branches, is a beauty to behold, but the casual passer-by, if insensible to the beauty of the flowers, may perchance be attracted by their sweet and delicate perfume. Farther along in a shallow wash where the waters occasionally take their way from the higher land, appears Chilopsis saligna in slender graceful form, swaying to every breeze. Its clusters of red flowers need not be seen to be aware of their presence, for their sweet fragrance is borne on the breezes far beyond that of most flowers. There are few desert flowers equally conspicuous in color and perfume, and few as well supplied with either as the desert willow. But where the way leads down into the bottom of the arroyo, almost hidden under the overhanging bank, one comes unexpectedly upon the beautiful "tronadora," to use its Spanish name. Few plants of the desert are more striking in their beauty than this, with its dark, deeply compound leaves and its conspicuous cluster of orange-colored flowers, which reminds one in their form and attitude of those of the trumpet-creeper, and well it may, for it is Tecoma starts, a member of the same genus. If we thread along still further through the tangle of "charnís" (Forrestiera) with its load of mistletoe, and "junco" (Holacantha) and "huisache," with lacy trimmings of the vine, Nissolia, where the dry stream bed is flanked by Trixis, and sometimes Tatalencho (Gymnosperma) on upward to where the steep banks of the arroyo give way to less precipitous rocky slopes and into the deeper cañon beyond, Asclepias linaria springs from the sandy wash at our feet with its sheaf of slender stems, each capped by its umbel of white flowers. Now just to the right where a limestone cliff faces the north and receives little light from the sun that scorches the ground just beyond, is a patch of resurrection plants with their star-like forms expanded to full view by the moisture acquired from the recent shower. The day before when we passed this same way these plants had coiled themselves together into compact balls and were hardly visible in the crevices of the rock. But with the drenching shower came the resurrection to renewed activity. Near at hand some shrubs are covered with a furry growth of grayish grassy-looking plants, which upon nearer approach are seen to be a dense growth of Tillandsia recurvata, a sort of Florida moss, which finds in the moister air of the canon floor or the mountain top the conditions favorable to its growth and it attaches indiscriminately to any woody plant that furnishes a convenient hold.
But of the many things that we brush by in this ramble we have not the time to tell, but in this narrow space of moisture between zones of perennial drought, occur ferns of the genera Pellæa, Notholæna and Cheilanthes. Under the neighboring rocks their prothallia are growing, and young sporophytes of all ages are coming on. Climbing out of the bed of the cañon in a few steps we find ourselves again among the ocotillos and the agaves and the cacti.
Among the shrubby plants none are so important as the guayule, the native name for Parthenium argentatum. It is one of the most abundant of all the desert plants, especially on the limestone slopes, and its grayish color gives a distinct character to the landscape where it abounds. A small shrub or dwarf tree, it seldom exceeds four feet in height or a stem diameter of four inches. Its leaves are covered with silvery hairs and its flowers are in inconspicuous heads of composite structure not over one fourth inch across. Its light seeds—one hundred would not fill half an ordinary thimble—are supplied with a papery bract by the aid of which they are driven easily by the wind. Maturing in late summer and autumn, the seeds are dropped to the ground beneath the parent plant, or by some strong gust of wind are borne to a distance, where some find lodgment in a sheltered spot—a crevice of the rock or the cover of some friendly shrub. Here, when the rain comes, it is kept moist for time enough to send down a long, slender, thread-like root before drought again overtakes it. After the fitful showers of summer have passed a long dry season awaits the young plant, so it behooves it to make as much root as possible while the growing conditions are favorable. These slender roots will make a growth of six inches in about a week, before the first true leaf has appeared lifted on the short stem half an inch high, and in six weeks the tap root has been observed fifteen inches long. Thus the plant insures itself against the dry season, and by hardening its stem and leaves, makes still further provision against the vicissitudes that await it.
And this example serves, doubtless, for many other desert plants. We find that the seedlings spring up in abundance under the shelter of bushes and cacti and other perennials. In fact, elsewhere there is almost no chance for the survival of a tender seedling, since the hot sun dissipates so quickly the moisture of even a heavy rain that the surface of the soil is again dry in less than a day. The chances of survival of a seedling are exceedingly remote, and considering the great number of seeds produced and distributed, probably only a very small fraction of one per cent, even germinate.
But interest in this guayule which covers the desert slopes is not alone in relation to its environment, but in the hule or gum which it produces, forming no small part of the rubber production of Mexico. Two and a quarter millions of dollars' worth of this product came from one district in one year recently and much more is following. Back in the middle of the eighteenth century it was discovered that the source of the rubber in the balls with which the Indians were wont to amuse themselves, was this guayule. As the Indians formerly did, so one now may extract this rubber in the same crude way by chewing the bark and rejecting the fiber until sufficient gum for the purpose has been accumulated.
That this gum is a by-product in the physiological processes of the plant and stored in its tissues in the form of granules, is not the least of its interesting features, for most of the rubber-bearing plants known to the public are trees yielding a milky fluid from which the rubber is obtained by coagulation. But in this case the rubber is not obtained by tapping, but by the immediate destruction of the plant.
Besides the mesquite and the greasewood and other shrubs that clothe the valleys and lower slopes, the steeper acclivities abound in Jatropha, Buddleia, Salvia, Bahia, Ephedra and many other woody plants, members of other genera to the number of a hundred or more, are scattered among the agaves, the palmas and the cacti up and down the mountainside.
One who has not sought these plants where they grow can have little idea of their number and variety, nor of their varied structural and physiological attributes which make for complete fitness in the stern environment of the desert. Here they grow and flourish where it would seem there is no chance for life. But they thrive in these barren wastes—league on league of plain and mountain, where there is neither spring nor pool nor forest shade, blistering heat and glare above and hot dry stones beneath, and find it sufficient.