AGE CYCLE IN PLANTS AND LOWER ANIMALS 



249 



viduals. Various investigators, prominent among whom is Klebs, 1 

 have investigated and analyzed the external conditions which 

 determine spore formation in the algae and fungi, and the results of 

 their work agree well with this idea. 







FIGS. 106-108. Formation of spores in lower fungi: Fig. 106, a terminal cell of 

 Saprolegnia producing zoospores; Fig. 107, A-C, three stages in the development of 

 the sporangium in Mucor; Fig. 108, branches of the sporophore of Penicillium, pro- 

 ducing series of conidia. From Coulter, etc., '10. 



While these forms in nature usually go through a more or less 

 definite life history in which vegetative growth or growth with 

 reproduction of new vegetative phytoids occurs for a time, and is 

 followed by the formation of spores and in many cases still later 



1 See Klebs, '93, '960, '966, '98, '99, 'ooa, 'oo&, '03, '04. 



