202 



It is rather interesting to find that Darwin considered this 

 question, and made a diametrically opposite guess. He thought 

 D. binata primitive, and the original type of leaf in Drosera as 

 elongated.* He did not perceive that these two suppositions are 

 incompatible. The so-called "two-forked" leaf of D. binata is 

 not forked — except in the variety D. dickotoma, where the lateral 

 arms are often once or twice branched — but the prongs of the 

 leaf are really upturned extremities of an enormously widened 

 blade, this being the very antithesis of the condition in D. filiformis 

 (of that in Byblis and Drosopliyllwji also). 



The round blades exhibited by both seedlings and adventives in 

 this species are probably reversions to a rotundifoliate ancestor. 

 They appear on mature plants, replacing the "full character" 

 leaves, when the plants are long subjected to a weakening process. 



Adventives of D. binata do not always show reversionary first 

 leaves, however. Buds on flower stalks and roots, being well 

 nourished, generally produce plants the first leaves of which are 

 crescentiform or fully binate ; i. e., of the adult type. This is 

 acceleration of development occasioned by abundant food supply. 



The tentacles of youthful leaves of all species are more inter- 

 esting than the leaf-shapes. A type of marginal tentacle with 

 the gland ventrally, rather than terminally, situated excited my 

 curiosity, for I found it in almost all species studied in their infancy, 

 even when the adult had nothing corresponding to it {e. g., D. 

 binata, D. linearis, D. intemnedia, D. capensis, D. Jilifonnis).'\ 

 In modified form it is found in adult D. rotundifolia, D. capillaris, 

 D. uniflora, and some other round-leaved species. Its presence 

 in other species is plainly atavistic. 



The youthful leaves oi D. intermedia, D. capensis, and D. lin- 

 earis are all round-bladed at first, thus differing from the adult 

 leaves, which are spathulate in D. interinedia, linear or linear-lan- 

 ceolate in D. capensis, and linear in D. linearis. In D. filiformis 

 of Massachusetts nepionic leaves occurred distinctly spathulate 

 and with atavistic marginal tentacles. 



In seedlings and adventitious plantlets from leaves and flower 



* Insectivorous Plants, p. 292. (Authorized Edition, Appleton. ) 

 •j" This form of tentacle is described in Rhodora, /. c, p. 270. 



