48 MOVEMENTS OF SEEDLINGS. 



afterwards cast off merely by the swelling of the 

 cotyledons. . . . The cotyledons can now assume 

 the function of leaves and decompose carbonic 

 acid ; they also yield up to other parts of the plant 

 the nutriment they often contain. When they 

 contain a large stock of nutriment, they generally 

 remain buried beneath the ground, owing to the 

 small development of the hypocotyl ; and thus 

 they have a better chance of escaping destruction 

 by animals. ..." 



" Our seedling now throws up a stem bearing 

 leaves, and often branches, all of which whilst 

 young are continually circumnutating. If we look, 

 for instance, at a great acacia tree, we may feel 

 assured that every one of the innumerable growing 

 shoots is constantly describing small ellipses ; as is 

 each petiole, sub-petiole, and leaflet. The latter, 

 as well as ordinary leaves, generally move up and 

 down in nearly the same vertical plane, so that 

 they describe very narrow ellipses. The flower- 

 peduncles are likewise continually circumnutating. 

 If we could look beneath the ground, and our eyes 

 had the power of a microscope, we should see the 

 tip of eacli rootlet endeavoring to sweep small 

 ellipses or circles as far as the pressure of the sur- 



i p. 556. 



