2l6 



PLANT LIFE. 



form. In many cases the plant ijrodnced is essentially- like 

 that which ga\'e rise to the spore. In others it is diflerent, 

 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 (•JIF S5. 320), the non- 

 sexual spores are pjroduced by one form only, and always 

 give rise to the other. 



311. Origin. — Non-motile sjiores are Q\\\\tx free, being 

 produced at the ends of branches sijecialized for that purpose, 

 or enclosed in a case called a spoi-aiigiu?//. (Jftcii the same 

 plant forms s[)ores by both methods at different stages in its 

 development. 



A 



a 



I 



Fig. 211. — Diagrams showing Ihe formation of an acropetal spore-cliain l>y bndding. 

 (7, tlie spore-producing hyplra ; l\ its terminal cell showing a bud which in r has ma- 

 tured into a spore ; //. the spore r lias budded, and so on. until in h live spores ha\e 

 been [ormcd, numbered in oj-der of their de\'elopnient. — After Zopf. 



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

 fined to the lower plants, and is espcciallv characteristic of 

 the non-a(|uatic fiingi. The branches producing spores may 

 occur singly, or, more comnionh', the\' are aggregated at 

 certain points, forming a s|i(_)re-brd (fig. 210). Ifthefimgus 

 develops its mycelium in the interior of a host, llic f>rmation 

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



