248 



SENESCENCE AND REJUVENESCENCE 



while in Mucor (Fig. 107, A-C) the sporangium arises at the end of 

 a specialized stalk, the sporophore, which grows out of the nutri- 

 tive substratum into the air, and in Penicillium still another type of 

 sporophore appears (Fig. 108). In other forms still other methods 

 of spore formation occur with various degrees of specialization in 

 the spore-forming organs, but everywhere the process consists in a 



FIGS. 102-105. Formation of spores in various algae: Figs. 102, 103, Ulothrix; 

 Fig. 104, a stage in the development of the zoospore in Vaucheria; Fig. 105, a filament 

 of Ectocarpus bearing a sporangium and at the left a more highly magnified zoospore. 

 From Coulter, etc., '10. 



disintegration of the plant body or some part of it into independent 

 cells. 



According to the conception of individuation presented in the 

 preceding chapter, return to the condition of the free-living, inde- 

 pendent cell must mean a decrease in the physiological coherence of 

 the plant individual, and it might be expected to result from con- 

 ditions which decrease the metabolism of the plant and so allow it, 

 or a part of it, to separate into its constituent units, the cell indi- 



