EVIDENCE FURNISHED BY SCIENCE OF LIKENESSES. 137 



FIG. 63. LEAF OF PEA. 



stemmed plants climb by the aid of these organs, is not a matter 

 requiring even a primer of botany for its verification. Now, plants 

 of very varied nature possess these organs ; and the question arises, 

 are these tendrils new and special organs in such plants as possess 

 them, or are they but modifications, like the home 

 of the Tortoise, of familiar structures ? Let the 

 science of likenesses reply, by directing our 

 attention to the general form of the leaf. Every 

 ordinary leaf (Fig. 62) consists, as we know, of 

 a stalk or petiole (/) and a blade or lamina (/), 

 and when we look at the apple leaf (Fig. 62), or 

 at a rose leaf, we may see at the point where 

 the leaf-stalk leaves the stem, two little wing- 

 like appendages, called stipules (s s), and which 

 are probably to be regarded as normal parts 

 and appendages of the leaf. These stipules are 

 large in the pansy tribe, and are also prominent 

 in the beans and peas, whilst in one of the 

 vetches (Fig. 66) Lathyrus aphaca, the Yellow 

 Vetch the stipules, as we shall see, may ac- 

 tually represent the leaves. In many other 

 plants, on the contrary, no stipules occur. 



Now let us examine the leaf of the Common Pea (Fig. 63). It 

 is a compound leaf, and we notice that the tendrils seem to grow 

 out at the sides and at the end of the leaf-stalk. The tendrils (tf) 

 here, are at once seen to exist in the place 

 of some of the leaflets (/), and are formed 

 by the end of the leaf-stalk also. We find 

 a very simple modification to be thus re- 

 presented ; certain parts of a leaf, in other 

 words, become altered to enable the plant 

 to climb. Tendrils here are "homolo- 

 gous" with leaflets and leaf-stalk. In the 

 lentil, it is the leaf-stalk itself which is 

 long drawn out to form the climbing 

 thread. The vine (Fig. 64) or passion- 

 flower may be selected as our next ex- 

 ample. Here the tendrils appear to be 

 formed in a very different fashion from 

 that seen in the pea. Apparently the 

 tendril (t t) in the vine and passion-flower 

 is a modified branch ; such an opinion being arrived at from a study 

 of the relations of the tendril to the stem and normal branches of 

 the plant. The Virginia Creeper likewise climbs by means of its 

 altered tendril-like branches. Once again we meet with a similar 



FIG. 64. TENDRILS OF A VINE. 



