2l6 



PLANT LIFE. 



form. In many cases the plant produced is essentially like 

 that which gave rise to the spore. In others it is different, 

 but sooner or later in the life cycle the same form recurs. 

 Variety of bodily form is common among the fungi, in which 

 it is called pleomorphism. Among plants showing well-de- 

 fined alternation of generations (*[^[ 55, 320), the non- 

 sexual spores are produced by one form only, and always 

 give rise to the other. 



311. Origin. --Non-motile spores are either free, being 

 produced at the ends of branches specialized for that purpose, 

 or enclosed in a case called a sporangium. Often the same 

 plant forms spores by both methods at different stages in its 

 development. 



a 



FIG. 211. Diagrams showing the formation of an acropetal spore-chain by budding. 

 a, the spore-producing hypha ; b, its terminal cell showing a bud which in c has ma- 

 tured into a spore ; d, the spore c has budded, and so on, until in It five spores have 

 been formed, numbered in order of their development. After Zopf. 



312. Free spores.- -The formation of free spores is con- 

 fined to the lower plants, and is especially characteristic of 

 the non-aquatic fungi. The branches producing spores may 

 occur singly, or, more commonly, they are aggregated at 

 certain points, forming a spore-bed (fig. 210). If the fungus 

 develops its mycelium in the interior of a host, the formation 

 of a spore-bed is often necessary to rupture the host, so that 



