l86 OUTLINES OF PLANT LIFE. 



nary buds. In both cases it is necessary that the cells to be 

 separated from the parent should be capable of growth — that 

 is, in the condition known as the embryonic phase (^ 215). 

 The reproductive organs produced by some plants are ex- 

 ceedingly complex and varied, while others form reproduc- 

 tive bodies in very direct ways. The reproductive bodies 

 themselves are generally very simple. In addition to com- 

 plex reproductive organs, there are sometimes accessory parts 

 by which the plant adapts its reproductive functions to the 

 conditions under which it lives. Among these accessory 

 structures are many, as among the flowers of seed plants, by 

 which the aid of other plants or animals is secured. 



259. Vegetative and sexual reproduction. — In all the 

 diversity of organs and processes two chief methods may be 

 distinguished, called vegetative reproduction and sexual repro- 

 duction. 



Vegetative reproduction consists in the formation of repro- 

 ductive bodies by processes of growth only. The modes in 

 which they arise are varied in detail, but consist essentially 

 in the production by the parent of a body, unicellular or 

 multicellular, which at maturity develops, under suitable 

 conditions, into a new plant. It is scarcely to be doubted 

 that the earliest methods of reproduction were vegetative, and 

 that sexuality has been acquired by a gradual adaptation of 

 cells previously devoted wholly to ordinary processes of 

 growth. 



Sexual reproduction consists in the formation of reproduc- 

 tive bodies by the union of two specialized cells, neither of 

 which alone is capable- of developing into a new plant. 



I. Fission and budding. 



260. Fission. — In single-celled plants cell division and 

 reproduction are practically identical, since shortly after 

 division occurs the two cells so produced separate and lead 



