5 



THE POPULAR SCIENCE MONTHLY. 



while the task which he set to himself was to answer the question, 

 " Why the Drosera caught such numbers of insects," the result has 

 "been the most valuable contribution to botanical literature which this 

 age has seen. Competent critics pronounce it more important than 

 his works on the "Fertilization of Orchids," and the "Movements 

 and Habits of Climbing Plants ; " and in scientific research there is, for 

 Mr. Darwin, no higher standard of comparison than to compare him 

 with himself. 



The greater part of the book is given to the record of observa- 

 tions on the phenomena shown by Drosera rotundifolia. This well- 

 known plant bears from two or three to five or six leaves, generally 

 extended more or less horizontally, but sometimes extending vertically 

 upward. The shape and general appearance are shown, as seen from 

 above, in Fig. 1 : 



Fio. 1. Dkoseea botunbifolia. Leaf viewed from above ; enlarged four times. 



The leaves are commonly a little broader than long ; the whole 

 upper surface being covered with gland-bearing filaments, or tenta- 

 cles, as Mr. Darwin calls them, from their manner of acting. 



A tentacle consists of a thin, straight, hair-like pedicel, carrying 

 a gland on the summit. Each gland is surrounded by a large drop 

 of extremely viscid secretion ; they average about two hundred on 

 each leaf, and as they glitter in the morning sun have given to the 

 plant its poetical name. The tentacles on the central part of the 

 leaf are short and stand upright, and their pedicels are green. Tow- 

 ard the margin they become longer and longer and more inclined 

 outward, with their pedicels of a purple color. Those on the extreme 



