The Journal of Indian Botany/Volume 1/April 1920/The Vascular Connections and the Structure of the Tendrils in some Cucurbitaceae
THE VASCULAR CONNECTIONS AND THE
STRUCTURE OF THE TENDRILS IN
SOME CUCURBITACEAE
By Kali Das Sawhney, M.Sc.
Professor of Biology, Islamia College, Peshawar.
During 1917 and 1918 the writer investigated the anatomy of a number of cultivated species belonging to the Cucurbitaceae. A few writers have already dealt with the subject, and special mention must be made of Tondera (4) who has carefully investigated the vascular connections of a number of species of this family, and Muller (3) who has worked out the anatomy of the tendrils. The writer has re-examined some of the species worked out by these writers. Their results have been confirmed in a general way. Since however these two papers are not easily available to the ordinary reader and many species investigated by the writer have not been investigated by these writers and in view especially of some interesting results obtained, it is proposed to give a brief summary of the results arrived at by the writer.
It is well-known that the vascular bundles in the stems of the Cucurbitacese are generally arranged in two rings of five bundles each. The bundles are usually known as bicollateral as they possess phloem towards the inside of the xylem in addition to the external phloem. The bundles of the inner ring are as a whole larger than the outer bundles. These facts should be borne in mind in the following description unless otherwise stated.
Another point to be remembered is the position of the various organs at a node near the leaf-axil. Usually a number of structures are met with there arranged in a transverse row. In Benincasa, cerifera, for example, in a ground plan of the node, beginning from the left, we found the following:—a tendril, a vegetative bud, a flower, a glandular structure looking like a rudimentary leaf. The last structure is absent in some species, and has a different form in some others. These differences would be indicated at the proper places.
Methods
In addition to free-hand sections other methods were also employed in the investigation. In some cases complete series of sections were prepared through the nodes to study the course of the vascular bundles. In other pieces of stem were macerated in a suitable medium. In some cases both methods were tried.
A few words may be said about maceration. Several chemical reagents were tried, but none was found satisfactory. Even boiling in tap water was found too drastic. Ultimately the pieces of stems with their attached organs were left in ordinary tap-water for a number of days—about five in summer and about ten in winter—and then the vascular skeleton was prepared by teasing out the softer tissues.
The following species were studied. The methods adopted are also indicated.
- 1. Benincasa cerifera Savi. Maceration.
- 2. Lagenaria vulgaris Scringe. Maceration.
- 3. Citrullus vulgaris Schrad. Free-hand sections.
- 4. Trichosaothes anguina Linn. Serial sectioning.
- 5. Trichosanthes dioica Roxb. Maceration.
- 6. Luffa acutangula Roxb. Serial sectioning and maceration.
- 7. Luffa pentandra Roxb. Maceration.
- 8. Cucumis melo Linn. Serial sectioning and maceration.
- 9. Cucumis momordica Roxb. Freehand sections.
- 10. Momordica echinata Linn. Serial sectioning and maceration.
- 11. Momordica charantia Linn. Serial sectioning.
- 12. Cucurbita maxima Duchesne. Maceration.
Of these species Tondera has figured the vascular connections of 1, 2 and 8 ; while Muller has figured the tendril-anatomy of No. 4.
After this preliminary account we may pass on to the details in the species investigated.
Benincasa cerifera.
In the axil [1] of the leaf we find a row of four different organs. From the left, we have a two-armed tendril, a vegetative bud which sometimes developes into a shoot, a flower and lastly a glandular structure standing erect and with margins rolled inwards, resembling a rudimentary leaf. (Fig. 1.)
The stem is five-angled as usual in the family. In mature specimens the inner and the outer rings of vascular bundles are very near each other and very nearly merge into one ring. (Fig. 2) The leaf-stalk is dorsiventral in its organisation, markedly so in its upper part where it has a distinct groove on its adaxial side. The number of vascular bundles varies from nine to eleven, those nearest the groove being the smallest. (Fig. 3)
The basal part of the tendril is radial in section, the number of bundles various from sis at the lower to ten in the upper part, and they are as a rule arranged in one ring. There is absolutely no trace of a ventral groove as is present in the petiole. (Fig. 4)
Both the branches of the tendril show a dorsiventral structure with a distinct groove on the apparently upper surface. The vascular bundles are five in number in the form of an arc open above as seen in a transverse section. (Fig. 5)
The vascular connections at the node are as follows : — The traces from the tendril, the vegetative bud and the flower-stalk all pass through the cortex and join the bundles of the inner ring. The leaf-stalk sends three traces into the cortex. Of these, one (median) passes down the internode below without anastomosing with any bundle at the node ; the two lateral traces join the two adjacent bundles of the outer ring, each with the one on its own side. One bundle of the inner ring, while coming from the upper internode, gradually decreases in size and ultimately ends blindly immediately above the node or just reaches it. The bundles of the inner ring anastomose at the node and this ring receives a bundle from the outer ring also to take the place of the one that has just ceased at each node. Thus at every node one bundle of the inner ring stops and a bundle from the outer ring joins the inner ring to take its place 1 while the place of the latter is taken by the median leaf-trace which passes down the lower internode without anastomosing. The gradual decrease in size of one of the bundles of the inner ring at each internode, as described above, is the cause of the dorsiventrality of the arrangement of the vascular bundles common in the family. (3)
It is clear from the above description that the bundles of the outer ring are really continuations of the leaf-traces, while the bundles of the inner ring are mainly cauline.
Lagenaria vulgaris,
The organs at the node beginning from the left are, a branched tendril with five arms very close to each other, a bud and a flower. The glandular organ is missing.
The vascular structure of the stem and the leaf-stalk is in general the same as in Benincasa cerifera.
1 This now inner bundle is not, however, a direct continuation of the outer bundle.
The basal part of the tendril is radial in section and has a ring (as seen in t. s.) of six to nine bundles which anastomose at different levels.
The arms of the tendrils are similar in structure to those of Benincasa cerifera.
The vascular connections of the tendril and the leaf with the stem are also similar.
ClTRULLUS VULGARIS.
The arrangement of organs at the node is similar to that in Ben- incasa, except that the flower is here replaced by an inflorescence- The tendril is two-armed.
The stem and leaf-stalk do not present any great differences from the first type.
The basal part of the tendril is radial with nine to twelve or thirteen bundles which are so arranged that large and small bundles alternate. The branches of the tendrils show the same structure as in the first type except that the bundles are seveD at the base diminishing to five near the apex.
Trichosanthes anguina.
The relationships of the organs at the node are the same as in Beni?icasa cerfera but the tendrils are four-armed.
The structure of the stem and the petiole is in general similar to that of the first type.
The basal part of the tendril in transverse section is slightly six- lobed and has six bundles in one ring. There is no trace of a ventral groove so that the structure is radial. The tendril-arms have a distinct groove and the bundles are arranged on the type of the petiole.
The vascular bundles of the tendril unite with the bundles of the inner ring of the stem, while the leaf-traces are connected with the outer bundles as described before.
Each tendril-arm receives three branches from three bundles of the tendril situated on the side on which the arm is given off.
In one case it was found that a ripe elongated fruit was apparently arising immediately below the branching point of a tendril. On cutting sections of the lower part of the tendril it was found that it was merely a case of fusion of the flower-pedicel with the basal part of the tendril. Goebel mentions a simlar case.
Trichosanthes dioica.
The arrangement of the organs at the node is the same as in the last species but the tendrils are simple. The structure of the stem and the petiole is of the usual type. The structure of the tendril however is dorsiventral throughout its entire length. At the base there are seven vasculer bundles which are reduced to five in the upper part. The traces of the tendril join the inner bundles of the stem just like the traces of the branched tendrils of other species. The middle leaf-trace passes straight down without anstomosing, while the lateral leaf-traces join the adjacent bundles of the outer ring of the stem.
LUFFA ACUTANGULA.
The arrangment of the organs at the node is as in Benincasa. The tendinis are four-armed, the branches arising along a very com- pact spiral.
The structure of the stem, petiole and the base of the tendril is similar to that in Benincasa cerif era .
The main arm of the tendril, the one which is in continuation of the basal part, has a structure similar to that of the basal part. The other arms have a petiole-like type of structure, having a distinct groove along the ventral side and horse-shoe arrangement of bundles.
The vascular connections of the various organs with the stem bundles are similar to those of Benincasa cerifera.
LUFFA PENTANDRA.
The arrangement of the organs at the node is as follows a four- armed tendril, a bud, an inflorescence and a triangular leaf-like ap- pendage bearing several circular facets.
The structure of the stem, petiole, the base of the tendril and the tendril-arms is similar to that of the corresponding organs in Benin- Gasa cerifera* The vascular connections are also similar.
CUCUMIS MELO.
The disposition of the organs at the node is as usual. The glandular organ is a circular faceted structure. The tendrils are simple.
The stem and the petiole do not show any unusual feature In their structure.
The tendril is dorsiventral throughout its entire length as shown by the presence of the groove and the horse-shoe arrangement of the bundles.
The vascular connections of the tendril-traces and the leaf-traces are the same has described for Benincasa cerifera.
CUCUMIS MOMORDICA.
The disposition of the organs at the node and the internal struc- ture of the various organs is in general similar to that in the last species. TENDEILS IN SOME CUCUKBITACEAE. 259
MOMORDICA ECHINATA.
Both simple and branched two-armed tendrils are found on the same plant. The disposition of the nodal organs is as in Citrullus vulgaris except that the leaf-like appendage is absent.
The stem and the petiole show the usual structure, the latter with only seven vascular bundles.
The base of the tendril, both in branched and unbranched speci- mens is four-Iobed and has four bundles only. The arms in the case of the branched tendrils, and the upper portion of the tendril in the case of the simple ones, possess a dorsiventral outline showing a dis tinct ventral groove and five bundles arranged in a horse-shoe manner.
The vascular connections are like those of Luffa acutangula and the rest, already described or to be described later.
MOMORDICA CHARANTIA.
Tendrils are all simple. To the right of the tendril at the node is a vegetative bud and next to this a flower. The glandular organ is absent.
The stem and the petiole has the usual structure.
The base of the tendril is four-lobed as in Momordica echinata. Ik has four bundles. One of them divides into two a little higher up and the tendril at the same time develops a groove, thus becoming petiole-like in its organisation.
The bundles of the tendril anastomose with the bundles of the inner ring of the stem.
CUCURBITA MAXIMA.
The tendrils in this species are four or five-armed. The vascular connections of the leaf-traces and the tendril-traces are the same as described for Benincasa cerifera.
Concluding remarks
It will be seen from what has been described before that or of the twelve species examined, four, i.e., Gucumis melo, Cucumis momordica, Trichosanthes dioica and Momordica charantia, have simple tendrils ; Momordica echinata has both simple and branched tendrils ; while all the rest, have branched tendrils.
The vascular connections of the stem with the tendril, the flower, the vegetative bud and the leaf have been examined in all except Citrullus vulgaris. The structure of the leaf-stalk and the tendrils at various levels has been examined in all except Cucurbitq
maxima. 
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The results are as follows : —
1. The vascular bundles from the flower, the vegetative bud and the tendril (whether simple or branched) in all the species examined unite with bundles of the inner ring of the stem at the node at which these organs arise,
2. Three bundles enter the stem from the leaf-stalk. The median passes straight down through the internode without uniting with any other bundle. The two lateral bundles unite with the adjacent bundles of the outer ring of the stem, one on each side.
3. At each node one of the bundles of the inner ring stops and its place is taken by a bundle from the outer ring. The bundles of the inner ring anastomose at the nodes.
4. The base of the tendril in all species with branched tendrils is organised radially the bundles being arranged in a ring and there being no groove, such as is present in the petiole. This is also true of the simple tendrils of Momordica echinata.
5. The tendrils in all the species with simple tendrils except Momordica charantia are organised on the type of the petiole with horse-shoe arrangement of bundles and a groove on one side through- out their entire length. In Momordica charantia the tendril is radially organised at the base and dorsiventrally above.
6. In all species the upper part of the simple tendrils and the arms of the branched tendrils throughout their entire length are organised on the type of the petiole. The main arm of the ten- dril which is a continuation of the basal part in Luffa pentandra is, however, radially organised. The upper part of this arm was un- fortunately not examined. It would probably possess a dorsiventral structure.
The following conclusions are drawn from the above results : —
1. The vascular connections and the structure of the basal part of the branched tendrils show that they are homologous with the ordinary shoots.
2. The arms of the branched tendrils and the upper part of the simple tendrils are homologous with the ordinary leaves.
3. The simple tendrils have been derived from the branched tendrils and therefore homologous with them. Species of Momor* dica show the transition in M. echinata possessing both simple and branched tendrils and in M. charantia possessing only simple ten- drils the base of the tendril is always radially organised. In other species with simple tendrils the modifications has gone still further and even the basal part has become petiole-like.
It may be stated that conclusions one and two are in general agreement with the conclusions of Muller and Tondera, but according
1968—34 to Goebel (1) the simple tendrils are modified prophylls while a branched tendril represents a prophyll adherent to an axillary shoot. My thanks are due to Professor S. R. Kashyap for much sug- gestive criticism and other help in the preparation of this paper. The work was done under his supervision in the Government College Biological Laboratory before the writer joined the Islamia College, Peshawar.
References to Literature.
1. Goebel, K. Organography of Plants. Eug. Tran.
2. Muller, O. Engler and Prantl's Pflaazenfamilien.
3. Do Untersuchungen uber die Ranken der Cucurbitaceen. Cohn's Beitrage zur Biologie, v (1887).
4. Tondera, F. Das Gefasbundelsystem der Cucurbitaceen. Sitzungsb, K. Acad. Wiss. Wien, CX1I, Abt. 1, pp. 23-59.
Explanation of figures. (1-5, Benincasa cerifera; 6-7, Momor- dica echinata.) xylem is shaded throughout.
1. Disposition of organs at the node, a, leaf ; b, tendril ; c, vegeta- bud ; d, flower; e, glandular organ.
2. Transverse section of steam in .'outline.
3. Transverse section of petiole in outline.
4. Transverse section of the base of a tendril in outline.
5. Transverse section of an arm of a tendril.
6. T. S. of the vase of the tendril.
7. T. S. of an arm of a tendril
- ↑ None of these structures is really axillary. In the Cucurbitaceae most of the structures occurring at this place are extra-axillary. The word is used merely for the sake of convenience throughont the paper.