The Sex and Generative Organs of Plants. 259 



The germ thus freed commences to form a growth down- 

 wards, i. e. the root, and to this succeeds the growth upwards. 

 More highly organized plants also, which form layers and 

 runners, follow in so doing the same type. 



In all these cases, the production of new individuals results 

 from nothing else but a peculiar alteration in consistency^ i. e, 

 in the form, relative fullness and closer apposition of the cells 

 and vessels, of which the parent individual is constituted. 



Sometimes the structure is thickened in particular spots, 

 where the smallest elementary parts press closer to each 

 other. Sometimes it becomes here and there weaker and 

 thinner, and frees itself from its original connections. The 

 separated sprout or the expelled germ immediately com- 

 mences an independent life df its own, increases in length and 

 breadth, and becomes at last an individual exactly like its 

 parent, which propagates itself in like manner. The whole 

 process, it is true, is subject, like every act of life to a regu- 

 lar order {Rhythmus.) It begins at a certain period, and at 

 a certain period is completed ; yet the growth and formation 

 of the young individual proceeds in a long uninterrupted con- 

 tinuous course, like the growth and ripening of a fruit. We 

 are therefore entitled to designate the want of distinctly 

 marked periods of development, and the gradual nature 

 of the changes which take place in the mother plant, as an 

 essential character in the process of reproduction in sexless 

 plants. 



In reality, such a new formation proceeds always only from 

 the upper growth of a plant, from the stem and the leaves, 

 or a portion of them, in which stem and leaves are organi- 

 cally united, and blended together, (the Thallus.) Never is 

 an individual developed in the same way from the system 

 that grows downwards, that is from the lower parts or the 

 root. Therefore, an individual newly formed in this way, 

 if it is to continue as an independent plant, must now 

 in the last place form of itself its root, which it has not 



