IN ANGIOSPERMAE. TENDR1LLOUS PLANTS 161 



Juvenile forms then occur in the climbing plants we have mentioned, 

 and they are distinguished by their plagiotropous growth and its conse- 

 quent different form of leaf, frequently also by a different phyllotaxy. We 

 have already seen above on page 94, in Vaccinium Myrtillus, how in 

 plagiotropous shoots arising from radial ones the */, phyllotaxy may 

 develop ; in the case of these climbing plants this change of position has 

 become inherited. 



2. PLANTS WITH TENDRILS. 



Most tendrillous plants have in their juvenile state no tendrils at all 

 or only functionless ones. The latter fact is of interest because it brings 

 again under our notice the arrest of organs. 



Let us first of all consider leaf-tendrils. We shall find here in 

 many instances that the young plants show all transitions from the first 

 foliage-leaves, which are not tendrillous, to those in which the tendrils 

 diverge in their configuration from that of the foliage-leaves and have 

 taken on the form of thin sensitive filaments. There are examples of 

 this in Corydalis claviculata, Adlumia cirrhosa, and others. In the 

 remarkable germination of Nepenthes ] we can follow clearly how the leaf, 

 constructed primarily only as a trap for animals and organ of assimilation, 

 gradually becomes also a climbing organ. On the other hand in Cobaea 

 and in the Leguminosae the transition is an abrupt one. 



Lathyrus Aphaca may be cited as an example remarkable in more 

 than one respect (see Fig. 76). The whole leaf-lamina has here been 

 transformed into a tendril. Upon the seedling plant some simple primary 

 leaves follow the hypogeal cotyledons as is the case commonly in Legu- 

 minosae. The first of them is usually a leaf without any segmentation 

 or with only a hint of this ; then come several three-pointed green scales, 

 the middle point corresponding to the lamina of the leaf, the two lateral 

 ones to the stipules. Next come foliage-leaves each of them with two 

 pinnules and asymmetric stipules. In the following leaves the leaf- 

 lamina is arrested and is seen as a small point between, the greatly 

 enlarged stipules which are now symmetric. In all the succeeding leaves 

 the lamina is transformed into a tendril. These rudimentary leaves 

 must be considered as the first functionless tendrils. We may assume 

 that in Lathyrus Aphaca the formation of leaves was originally as in 

 other species of Lathyrus, that only the terminal portion of the leaf 

 had the function of a tendril, that the pinnules were then suppressed and 

 in consequence of this the stipules attained their exceptional size. 



The formation of leaves in Lathyrus Ochrus- is very peculiar and 



GOEBEI, 



1 Goebel, Pflanzenbiologische Schilderungen, ii. p. 98. 



2 Lathyrus Clymenum and L. mauritanicus show the ?ame features. 



