The Journal of Indian Botany/Volume 2/June 1921/Some Observations on Cycas Revoluta and C. Circinalis growing in Lahore

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SOME OBSERVATIONS ON CYC AS REVOLUTA AND C. CIRC1NALIS GROWING IN LAHORE.*

By Shiv Ram Kashyap,

Professor of Botany, Government College, Lahore.

The observations described in this paper on leaf-clusters and ovules were made on plants of Cycas revoluta and C. circinalis growing in the Government College Botanic Garden and the Lawrence Gardens, Lahore, Some plants were planted in flower pots and were kept constantly under observation. Cycas revoluta is very commonly culti- vated in Lahore gardens but C. circinalis is not so common. The writer has not come across any male plant of Cycas revoluta in Lahore or in its neighbourhood, all the plants being female. It i3 propagated by means of buds which grow on the underground or aerial parts of the stem. These buds when detached and planted grow into new plants which are naturally female. A few years ago the writer obtain- ed some seeds of this species from Japan and these have produced some plants, but the latter have not as yet produced any flowers. Cycas circinalis is represented by many female plants but so far as the writer is aware there is only a single male plant in this locality, growing in a tub in the Lawrence Gardens. The female plants bear buds in fairly large numbers by which the plant is propagated, but the male plant has never produced any bud and therefore it is impossible to increase the number. Only one male cone is produced each year. It is formed during the rains and ripens towards the end of the rainy season, in August. The longest one measured during the last few years was more than eighteen inches, and the thickest, this year 1920, was nearly twelve inches in circumference at the thickest part.

Leaf-clusters of Cycas revoluta. — One series of observations on Cycas revoluta was meant to find out the interval between the suc- cessive leaf-clusters. Coulter and Chamberlain, in the recent (1917) edition of " Morphology of Gymnosperms " state : — " In Cycas revoluta it is said that a crown is formed every other year, but information in regard to the duration of the crowns, as they occur in the field, is scanty and uncertain." The observations recorded in this paper throw light on both these questions. No information about these matters is given in Chamberlain's recent book " The living Cycads."

Seedlings grown from seeds showed what is well-known, that the leaves at first appear singly and later on the number is gradually increased to two, three and more.

• A paper read before the Indian Science Congress at Calcutta. February, 1921. Ten plants were propagated by buds from the female plants growing in the garden, and were kept in pots under uniform condi- tions. Observations were commenced when the plants were five or sis years old. All the plants except No. 1 were in pots of the same size.

The former was in a large pot, it was the largest and probably the oldest. The pots of three plants got broken once at different times and were changed at once. It is however unfortunately not recorded what Avere the numbers of these plants. As is well known all the leaves do not appear quite simultaneously, but they arise gradually in some spiral, though the whole cluster is one unit.

The foliage leaves are always followed by scale-leaves. The number of leaves in each cluster in these plants varied between 6 and 20, the largest number being found in No. 1. In the rest the varia- tion was not so great. None of these plants has so far produced any sporophylls- The following table gives the times at which the clusters of foliage leaves appeared during the two years for which the plants were kept under observation. The formation of the cluster is indicated by an asterisk under the month in which it was unfolded.

1 Took a long time, about a month to unfold, Ordinarily the clusters iu all plants unfolded within ten days.

9 Stopped unfolding after a few days and the leaves fully opened only in the beginning of April, 1917 ( Vide entry there).

3 Ouly two leaves appeared at this time. Three more appeared after middle of July when the former were almost fully expanded. No scales were formed after the first two. The five thus belonged to the same cluster, the last three being for some reason or other delayed in their appearance.

The peculiar behaviour of the second clusters of No. 3 and 8 is apparently due to cold. The distinction between two clusters is easily determined by the formation of the scale leaves at the end of each cluster. The formation of the first cluster of No. 9 was thus spread out over one whole month, with a break in the middle.

In both years the position of the asterisk, under the first, second

or third letter of the month indicates that the cluster unfolded in the

beginning, middle or end of the month respectively.

It would be seen that the number of the clusters formed by the

ten plants during the two years were as follows :—

It is clear that the largest and probably the oldest plant formed only one cluster each year. The rest formed one, two or three, and all of these formed more than one in at least one of the two years. From these observations and others given further on in the paper made on much older trees which were growing on land in the garden, it will be seen that in young plants more than one cluster is usually pro- duced each year, while older plants produce only one cluster every year and still older ones produce clusters every other year or even at longer intervals. It may be mentioned also that it is difficult to give the exact age of the plants as the time during which the buds had remained attached to the parent plants is not known.

Another series of observations was undertaken on four large plants growing in the Botanic Garden. These are certainly more than twenty years old at the least. All of them produced cones in May 1919, and the following measurements were taken in October 1919. The girth is about the same throughout the whole length of the stem except at the very base where it is a little smaller.

The trees were kept under observation from October 1918 to November, 1920. The following was the sequence in which the foliage leaves and sporophylls were arranged with the time of appearance where known:—

The number of foliage leaves in each cluster was usually about sixty, and the number of sporophylls in each cluster varied between 120 and 170. It will be seen that there is no invariable alternation between the foliage leaves and the sporophylls though in many cases it is distinctly present. Again a cluster of foliage leaves appears usually after about eighteen months, though a cluster of sporophylls appears before the second foliage cluster in the meantime. We can say that usually one cluster appears every year whether of foliage leaves or sporophylls. Plant No. 2, however is very curious in this respect. It produced a cluster of foliage leaves in April and immediately after that a cluster of sporophylls about the end of May. Even now its activity was not quite exhausted and it produced another cluster of foliage leaves in November, 1920 when the other three trees showed no sign of forming any leaves. This behaviour is quite unusual but the cause of this excessive activity is not known.

In No. 4 three clusters of green leaves were visible below the cone, but in the others only two such clusters were present. The leaves below them had all died and therefore been cut away. On the basis that a leaf cluster appears every other year the age of a leaf cluster would thus be from four to six years.

Ovules of Cycas Revoluta.

As has been mentioned above there are no male plants of Cycas revoluta anywhere near Lahore. Naturally therefore one would not expect ripe seeds on the female plants. It is interesting to note however that ripe ovules, with fully formed endosperm and archr- gonia but without embryos, do occur occasionally. Le Goc has studied the same phenomenon in Cycas Bumphii in Ceylon. (Ann. Roy. Bot. Gard. Peradeniya, 1917, 6). He also finds well-developed ovules in that species though he did not see any male plants in the locality. He thinks that the development of the ovules is due to the influence of foreign pollen which he found in the pollen-chamber, obviously implying that the presence of the pollen grains is necessary not only for the formation of perfect seeds but also for the full development of the ovules. Without going into a discussion of this question it may be stated that in Lahore a very great majority of the ovules of Cycas revoluta shrivel after some time and only a few occasionally develop the endosperm and archegonia. It has not as yet been determined whether they receive any foreign pollen or not. There are a few male and female plants of Zamia growing near these plants of Cycas revoluta and a male plant of Cycas circinalis is growing in a tub at some distance. Although the female plants of Zamia do produce a few ripe ovules and seeds, the female plants of Cycas circinalis growing in the garden have not so far been seen to form ripe ovules or seeds. The connection of the development of the ovules of Cycas revoluta with foreign pollen, if any such connection exists, will be investigated at an early date.

The ordinary ovule of Cycas revoluta which has not fully deve- loped is more or less spherical with the sides flattened or depressed and possesses a notch at the tip. The ripe ovules met with on the same plants are very much larger, do not show any flattening of the sides, and but are rounded and gradually taper towards the apex which is very distinctly acutely pointed. This last character is very curious especially because in the ripe seeds obtained from Japan the tip shows the usual notch, or at least there is no tapering at the upper end. {Vide fig. 1.)

Another interesting point in this species is the occurrence of in- termediate forms between the sporophylls and the scales. The sporo- phylls, as is well-known, are pinnately divided organs in which the lower pinnae are replaced by ovules and thus correspond to the foliage

leaves, but of course are smaller, brown and whoolly. The sporophylls

Fig. 1.

formed last in the cluster remain sterile, their pinnae remain small,

the ovules are absent, and the pinnae are restricted to the upper part only. This reduction gradually leads to the sharply-pointed scales without any trace of the pinnae, but there is a complete series of in. termediate forms between the two extremes. The sterile intermediate forms very much resemble the sporophylls of Gycas circinalis without the ovules. {Vide fig. 2.)

Cycas Circinalis.

The accompanying photograph shows a very curiously branched tree of Cycas circinalis. It is growing in the Lawrence gardens. Lahore. The tree is known to have been growing there for more than thirty years and on the basis of one leaf-cluster every other year is more than eighty years of age. The history is that the apex was cut off at the place were the first bifurcation is seen and a scar is present at the fork. But after that the tree has not been interfered with. The repeated dichotomies form a very interesting feature of the plant and remind one of the fossil Cycadophyta like Wielandiella. 1 Four distinct dichotomies can be traced from the base

Vide Scott. Evolution of Plants, page 89. to the apex along one side of the tree. Another curious feature of the tree is that at some places the female sporophylls do not arise on all sides of the growing point as is normally the case but are developed only on one side. This may possibly indicate a tendency to variation in the position of the female cone from terminal to lateral, but nothing definite can be said about this matter without further investigation.

Since writing the above the writer has seen two more specimens of apparently the same species growing in the Royal Botanic Garden at Calcutta which are also branched in the same way. It is probable that the dichotomy is not real but only due to the growth of some of the buds which are so common on the stem of this plant. It may also be mentioned that Brandis (Indian Trees) says that Cycas Rumphii is often branched.

Literature cited.

1. Brandis. Indian Trees.

2. Chamberlain. Living Cycads.

3. Coulter and Chamberlain. Gymnosperms, 1917.

4. Le Goc. Effect of Foreign Pollination on Cycas Rumphii, Ann. Roy. Bot. Gard. Peradeniya, 1917, 6.

5. Scott. The Evolution of Plants.

Description of Figures.

1. Sporophylls of Cycas revoluta with unripe and ripe ovules.

2. Transition from a sporophyil to a scale.

3. Cycas circinalis showing peculiar habit.

Fig. 3.