GERMINATION. 143 



ary leaves did, the growth of the plant is necessarily more 

 rapid. 



It is important then to take all possible means of favor- 

 ing the growth of the second pair of atmospheric leaves. 

 As the power of absorbing food from the atmosphere and 

 soil increases with every fresh growth of leaves and fibres, 

 and is necessarily very feeble in the beginning, when the 

 plant is in the cotyledonary stage of development, it is ob- 

 vious that the beds must be kept carefully weeded, and 

 where the young plants are very much crowded together, 

 the feebler must be removed, in order to encourage the 

 growth of such as are more vigorous. 



Perennial plants lose their sexual organs when they have 

 served them but once, and develop others each year ; but 

 vertebrated animals, such as mammalia, and birds, pre- 

 serve those with which they are provided. In all the in- 

 ferior orders of animals, these organs have their times of 

 repose and periods of activity. 



" The period of ovulation is to animals what flowering is 

 to plants } and, indeed, few phenomena are more interesting 

 to the student of nature than those exhibited by animals at 

 the pairing season. Then their physiognomy is the most 

 animated, their song' the most melodious, and their attire 

 the most brilliant. Some birds appear so different at this 

 time, that zoologists are always careful to indicate whether 

 or not a bird is represented at the breeding season. Similar 

 differences occur also among fishes and other animals whose 

 colors are then much brighter. "* Thus in early spring, 

 when plants put forth new leaves and flowers, we have re- 

 newed at the same time the hair, feathers, scales, horns, 

 and other external appendages of animals. Both are alike 



* Principles of Zoology, by Louis Agassiz. 



