IN ANGIOSPERMAE. TENDRILLOUS PLANTS 163 



portion or leaf-base. Subsequently development proceeds in the way above 

 described. The arrest of the stipules has certainly a causal connexion with 

 the broadening of the whole primordium of the leaf; they have become 

 superfluous as protecting organs for the stem-bud because this function 

 is performed by the broad leaves themselves. The broadening of the 

 leaf-surface will however allow the plants to grow up quickly and to 

 overcome their rivals, and I should suppose that these species grow upon 

 densely clothed grassy spots, or in hedges, in not very strong illumination. 

 In this way I believe we can follow the changes which have taken 

 place here. 



Lathyrus Nissolia behaves in the same way, only in it the uppermost 

 leaves develop no tendrils ; the seedling produces, as in Lathyrus Ochrus, 

 small lanceolate simple primary leaves provided with rudimentary stipules. 

 There seems to me to be at the present time no positive foundation 

 for Darwin's hypothesis l which derived this species from an original 

 twining plant which became a leaf-climber, then lost the branching character 

 of its tendrils, and finally also their capacity for rotation and their 

 sensitiveness, with the result that the tendrils again became leaf-like. 

 Darwin assumed also a double change in the construction of the stipules. 

 It is possible that Lathyrus Nissolia sprang from a tendrillous plant, but 

 I do not see any advantage in assuming so complex a path of development 

 as Darwin does ; a comparison with Lathyrus Ochrus seems to me to 

 indicate a much simpler one. 



I may in conclusion cite one more case which derives interest from 

 the peculiarity that the primary leaves have the function of tendrils. Darwin 

 has shown 2 that Tropaeolum tricolorum produces no leaves up to a height 

 of two to three inches ; it only bears ' filaments,' sensitive to contact, which 

 in the upper part of the stem pass over into complete leaves. These 

 ' filaments ' are merely primary leaves, and their taking on the function of 

 tendrils is evidently due to the extreme thinness of the shoot-axis which 

 necessitates the production of supporting organs at a much earlier period 

 than is the case with other plants bearing tendrils. The seedlings of the 

 plant which I examined produced only few ' filaments ' before formation 

 of complete leaves occurred. The filaments are elongated primordia of 

 leaves upon which no separation into stalk and blade has as yet taken place. 

 Higher up on the plant a blade becomes visible. A feature exhibited by 

 Tropaeolum majus may be here briefly mentioned. Whilst most species 

 of the genus have no stipules, although they evidently possessed them 

 originally, Tropaeolum majus has them on the first two leaves but with 

 a reduced character ; sometimes one is wanting and they do not always 

 appear in the normal position. 



1 Darwin, Climbing Plants, p. 154. 2 Darwin, 1. c. p. 47. 



M 2 



