Popular Science Monthly/Volume 35/July 1889/Fungi II

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FUNGI.

II.—MICROSCOPIC FORMS.[1]

By T. H. McBRIDE,

PROFESSOR OF BOTANY IN THE UNIVERSITY OF IOWA.

THE microscopic world is ever fair. In every department of research we revert to our instruments, certainly expecting to be charmed by beauty, whether of movement or mechanism. Rarely are we disappointed, certainly not in the realm of organic form. Here everything is beautiful, and, as the heavens to the astronomer, everything is clean. Even the rudest fungi offer no exception. In them the microscope finds no exception to the law of beauty. The simplicity of structure noted in the previous article runs through nearly all, only varied a thousand times; but whether mycelial thread or spores, one or other or both conjoined, the result, as we hope by illustration here to show, is always symmetry and elegance itself.

To begin, let us revert to the lilac-bush, whose whitened leaves may readily afford illustration of mycelial webs and threads. By September, if not sooner, the entire foliage will have taken on its peculiar whiteness as if thickly dusted with chalk or flour. On certain leaves, however, appear suspicious-looking dark-brown specks or grains, very small, but plainly visible to the naked eye. Removing some of these granules to the microscope, we find the field filled with tiny sculptured spheres ornamented with a profusion of long, interlocking filaments, starting out like so many extended radii of each sphere. A gentle pressure on the cover-glass breaks the sphere, and forthwith (Fig. 1) a dozen tiny sacs appear, each packed with, transparent oval nucleated spores, just such spores and quite such sacs as appeared in the fruiting surface of the morel, and we are ready with the botanist to call the granules fruit. Who could have guessed the contents of that sphere? But look again at those radiating ornamental filaments. Trace to its distal end a single ray, and see the grapnels by which the fertile globule we have studied holds fast to the surface of its host through storm and flood. Notice the elegant curves, the symmetrical branching, fit model for the artist in arabesque or filigree! What more beautiful or more efficiently suggestive! (Fig. 2 a.)

Such is the lilac blight; but now that we have discoverd one such fungus, we may carry our inquiries to almost any extent. The neighboring cherry-tree will afford similar material for study and admiration. Here the appendages are simpler, and the fruit itself contains but a single sac with spores (Fig. 3 a). The poplars and the willows show spherules whose appendages are simple hooks, so that the fruit is a minute bur of the teazel sort, fit for fairy carding (Fig. 2 b). The oak-leaf and the hazel bear appendages simpler still, the appendages being straight and needle shaped, ray-like, actinic; Phyllactinia Léveillé named it—lea-fray—the needles starting like rays of light from some effulgent center (Fig. 3 h).

During the early days of autumn we can hardly go amiss for the appendaged fungi such as just described. In the woodland, the pastures, by the road-side, in shade and in sun, a thousand white-flecked leaves attract the appreciative and only the appreciative eye. Minuteness removes from ordinary ken—and the world goes on! Besides, these parasites are not especially harmful, at least in the phases described, to their presumably unwilling hosts. The pea-vine and the rose-bush may sometimes suffer, but generally the leaves attacked have pretty well done the season's work before the parasite attains its maximum, so that man's interest in the matter is not specially affected. There is, however, another and different set of leaf-fungi whose parasitism is decidedly more intimate, and consequently destructive of the host-plant, suicidal as such a policy would seem to be. These latter, as indeed all the fungi already cited, are known as blights, and as such some species are already famous. The potato murrain, which has its place in civil history, is a very pretty little transparent branching fungus, so delicate that a breath destroys it. First becoming notorious in 1845, and during the famines of 1846 and 1847, it has been found and studied in all parts of the world for the forty years succeeding. The lilac fungus is content to spread its mycelium over the surface of the lilac-leaves, absorbing its nourishment from the surface cells; but the potato mold. the Phytophthora infestans of the books, seems to reach every cell and every tissue, so that a whole potato-field once infested will go down as if smitten by the frost of night. Kindred fungi are upon many of the plants about us. Peronospora viticola attacks the leaves of the grape. In wet seasons it is not uncommon to see the wild grape-vines along our western streams completely white with this overwhelming assailant, nor are our Concord vineyards ever quite exempt. The mycelial filaments thread the soft interior tissues while fruiting hyphæ come forth in delicate tufts or pencils through the open stomata on the under surface of the leaf. It is pleasant to think that weeds of various kinds suffer from similar fungal invasions. Thus goosefoot (Chenopodium, sp.) bears every spring upon its earlier leaves a tiny parasite, which seen under our lenses seems a miniature forest, while the fruit masses itself in violet tinted patches plainly to be seen by the naked eye.

Even the evergreens, the cone-bearers, that ancient race of hardy conservatives, are compelled to pay tithes and tribute to these all-assailing Vandals. I suppose the cedars of Lebanon are not exempt! At all events, who has not seen our native cedars bending after some warm shower in June with orange-colored fruit, beautiful, but to the cedar costly as it is fair? (Fig. 4 a.) Cedar-apples, men say, and they are not a few who would insist that the cedar is actually blooming and fruiting. Such fruit has actually been planted—vain expectation. Cedar-apples are but the excrescences caused by the persistent development of a fungus parasitic upon branch or leaf; they are receptacles from which the fungus throws out at a favorable moment gelatinous masses of orange-colored spores (Fig. 4 b). No fruit of the cedar are apples such as these, fruit rather of the cedar's malignant foe. Trees are sometimes seen whose crop of "apples" becomes so heavy that disaster almost to extinction marks successive years. Strange to say, the cedar does not bear its affliction alone. The hawthorn has a part in the matter, and on its leaves are borne fringed cups of fungal fruit supplemental to the cedar's parasite, just as the cluster-cups on the barberry-leaves are congeners of the rusts on fields of standing grain. In fact, with these microscopic forms parasitism is the rule, whether as affecting the vegetable world as we have seen, or in more insidious guise assailing the animal as well, when bacteria and bacilli in phantom myriads appear to baffle surgery and sanitary science. Here, as has been well said, is "the arrow that flieth by day; the pestilence that walketh at noonday." The discussions of a decade have rendered these organisms familiar, at least by name, to every reader. Every wise physician is an experimenter in the field. A new literature has grown up, to which the scientific world makes daily contributions, and bacteriology is hailed the latest phase of biologic science. Nevertheless, the subject is as yet only touched upon. We have simply begun to find out how to study these minutest forms, some of which may yet be hiding beyond our utmost microscopic vision.

But the most remarkable group of fungoid organisms remains yet to be considered—remarkable alike because of the innate novelty and beauty of the objects themselves, and because of the difficulty which seems ever likely to attend any effort to fix exactly their place in classification. Among English writers the organisms in question are called slime-molds; in science they have received as a group different appellations. The slime-molds are PSM V35 D373 Fruit of the lilac blight.jpgFig. 1.—Fruit of Lilac Blight, x 300. sufficiently common in all the wooded regions of the globe, although receiving less attention on account of minuteness and unobtrusiveness. With most of the species it is a plain case of "seek and thou shalt find." Some, however, are quite large, as, for instance, one of the simplest appearing often in summer flowing up between the planks of our familiar board walks, for be it understood at the outset that the slime-molds are, in one stage hi least, soft, protoplasmic bodies possessed of locomotive powers, changing form with protean incertitude, and position with nonchalance far from reassuring. The species in question appears then, in quantity, a patch of brownish, frothy-looking matter, not attractive. Scrape it away, and probably more will take its place, furnished forth from the moist, dark chambers underneath. Leave it a few hours, and you return to find a mass of purplish dust, overarched, perchance, by a porous crust of yellowish color and fragile structure. This dust is fruit, spores we may say, and we wonder what may be the destiny of spores formed in so strange a fashion. Place a few of these spores in a moist chamber, and in a short time each germinates and produces—a mycelial thread? Not at all; on the contrary, a protoplasmic particle, not to be distinguished from that other protoplasmic bit men call Amœba. When these Amoebae, produced by the germinating spores, have for a time pursued each his individual way, all under favoring circumstances reassemble, coalesce, actually blending, in most PSM V35 D374 The lilac blight.jpgFig. 2. cases, to produce a new slime-mold in all respects comparable to its polymorphic ancestry, a new motile organism ready once more to break up into spores and fruit, and so continue its never-ending cycle of purposeless existence. I say purposeless, for there seems to be no outlet, no outlook toward anything better or higher. Its relations look backward, not forward, and we connect it with the lowest forms of animal life more easily than with anything else. Hence the difficulty of the systematist. Animals they can hardly be, for nowhere else in the kingdom are animals reproduced by spores, to say nothing of the forms of fruiting described later on. We call them for convenience fungi; yet, while some fungi are destitute of mycelium, and some produce swarm spores or motile naked amœboid spores, still in no instance do these behave as in the slime-mold.

It is interesting to notice the gingerly manner in which naturalists in their discussions approach these forms. Sachs throws in a chapter, nowhere in particular, a sort of addendum on Myxomycetes. De Bary, the lamented, gives us his masterpiece on fungi, "including the Mycetozoa," and in speaking of their relationship says, "For various reasons, which, according to the knowledge at hand, have from time to time been more or less closely worked out, I have, since 1858, placed the Myxomycetes (slime-molds) under the name Mycetozoa outside the vegetable kingdom, and this I still consider their proper place."[2] He does not call the organisms animals, be it observed. If a zoölogist chooses to do so, De Bary makes no objection. Meanwhile, Saville Kent, zoölogist, encouraged probably by De Bary's position, comes forward in PSM V35 D375 Leaf ray fungi.jpgFig. 3. his "Manual of Infusoria" and claims the whole series as animals; while Cooke, as representing the English botanists, says, in the introduction to "Myxomycetes of Great Britain," "It is unnecessary to attempt any controversion of the proposition once made, but soon ignored, that these organisms are more intimately related to animals than plants."[3] And Saccardo, in his great work now appearing, "Sylloge Fungorum," enumerates and describes the Myxomycetes with the rest.

But while systematists thus differ as to the place the slime-molds should have in classification, we need not hesitate to enjoy their beautiful forms. They are, whether we know what they are or not. The sidewalk species is very strange, and the transition from slime to dusty spores would be incredible did we not witness it. Stranger still, however, is the case of a species often brought in midsummer from the woods. Here, as the object comes from the forest, is a mass of yellowish slime without apparent structure or parts, "without form or comeliness." We lay it upon the laboratory table, shut it up in a box, if you choose, and a few days later examine to find no end of structure. Every particle appears to have passed into the composition of definite and elegant machinery. A perfect honey-comb now lies upon the bit of rotten wood, the original support, each cell capped with a filmy lid which seems all too fragile, and which, opening here and there, discloses a powdery, fluffy mass within. Brought to the microscope, the contents of each cell spread out in fruit, in spores and banded filaments, "elaters" called, to whose beauty our drawing (Fig. 5) pays but distant tribute. Golden is the color, sculptured are the spores, and twisted are the filaments with many a delicate spiral wound, the coils running transverse to certain finer striæ, as if the whole structure did but make appeal to some aesthetic eye. Slime-mold it was before, Trichia chrysosperma now, and, so far as may be seen, simple evaporation has wrought the change.

Fig. 6 illustrates the fruit of another slime-mold which, during the present year, has been extremely common in this vicinity. Abundant rains during the summer were, perchance, the stimulating PSM V35 D376 Cedar apple and spores.jpgFig. 4.—"Cedar-Apple" and Spores—the latter highly magnified. cause. On oak-stumps of four or five years' standing there appeared glistening patches of the size of one's hand, by no means attractive to the casual observer; rather the reverse. Presently the entire mass heaped itself up, becoming, say, four tenths of an inch in depth; a thin film covered all, and desiccation began. Shortly the entire mass had been transformed. Hundreds of slender columnar receptacles, each mounted upon the most delicate little, black, shining pedicle or stalk, and crowded with spores, completely replaced that mass of slime, leaving scarcely a trace. The upper film breaks away, and a thousand delicate, plume-like structures wave a diminutive forest (Fig. 6). Each tiny stalked receptacle is a spore-case with lace-like walls of richest color, and is at first packed with unicellular sporules of the same deep tint. The entire fruit resembles somewhat a stamen, hence the name, Stemonitis (like a stamen). Other fungi, of the same type as

Left or right floating image with optional over or under description stemonitis, only more delicate still both in form and color, are not infrequent. They are everywhere in the woodland—on leaves and sticks that lie close upon the ground, upon a thousand humblest things. Such forms are the Comatrichæ, Arcyriæ, Cribrariæ, etc. PSM V35 D377 Spores and elaters of trichia chrysosperma.jpgFig. 5.—Spores and Elaters of Trichia chrysosperma. Highly magnified. The arcyrias form their spores and the net which contains them all in a delicate spherical or obconical receptacle.[4] At maturity the upper part breaks away and the elasticity of the contained structures forces them out as a most airy puff, from which the spores may be driven by the wind while the base of the original envelope remains as an empty cup. Sometimes the entire structure is mounted upon a slender, polished stalk of appreciable length, and the whole colony of sporangia stand as tiny salvers whose shadowy contents rise like incense-wreaths. To find a rosy field of Arcyria puniceum, to safely box it and lodge it in one's collection, is enough to give a man joy, even of the aesthetic sort, from Sunday to Sunday. The tints in all these fruits are just right: they are the grays, the olives, the brick-reds, the browns, and yellows.

Of these that produce their fruit thus in spherical or cup-shaped receptacles, some are giants among the rest. One, very common, imitates the Lycoperdons, or puff-balls, and that so closely as to have deceived the botanists themselves. It has been named Lycoperdon again and again, and even carried over the whole tribe with which it is related into the order Gasteromycetes—the puff-ball order. The student finds a row of little spheres, ashy or rosy in color, about as large as bullets, resting side by side on some bit of rotten stuff in the woods, and forth-with thinks about Lycoperdon pusillum, or possibly some new species, and not until after much investigation and groping, and probably some outside assistance, does he at length reach the "true inwardness" of Lycogala.

The more we study these wonderful organisms, the more surprising it seems that two such very different phases should coexist in the same organism and succeed each other so abruptly. We no longer wonder at the perplexity of the systematists, and we can PSM V35 D378 Stemonitis fusca.jpgFig. 6.—Stemonitis fusca. Central figure x 2; detail and spores more highly magnified. but admire the reckless courage of Saccardo, who discusses the slime-molds in his volume vii, "Sylloge Fungorum" along with other myceliumless forms, and says-never so much as "By your leave."

Before the vision of the biologist there rises ever more that weird limbo where "men" appear "as-trees walking." Whether, as in that elder case, experience may bring clearer vision, time alone can tell. Plant and animal have doubtless somewhere a common starting-ground. Toward that common origin the Myxomycetes undoubtedly point. They PSM V35 D378 Arcyria punicea.jpgFig. 7.—Arcyria punicea. Detail and spores highly magnified. are not it. They seem rather to represent an independent twig near the base of the great tree of life, a branchlet whose departure was absolute as ancient, developing with no respect to any other organic thing, and soon reaching the limit of that particular possibility. Perfect in themselves, we may look for nothing further in that direction. Nature herself has written, "No thoroughfare."

In conclusion, we may notice the question of utility which doubtless rises in some minds. To what end are all these microscopic bits of stuff organic thus hidden from ordinary ken? To such a query no real answer can be given. Our systems of economics are nowhere sufficiently refined, our tests of value show no balances whose delicacy trembles to a case like this. What know we of Nature's infinite equipoise? Such organisms are their own excuse for being, and, if by any chance they serve at length the aesthetic sense of some creature intellectual, his is the good fortune; their destiny waxes not nor wanes.

 

  1. Illustrations from drawings by M. F. Linder and the author.
  2. De Bary, "Morphology and Biology of Fungi," p. 478.
  3. Cooke's "Myxomycetes of Great Britain," introduction, p. iii.
  4. Stemonitis also has at one time in its development a delicate peridium around each sporangium. This, however, soon vanishes.