32 REPRODUCTION 



intervals during twenty-four or forty-eight hours, the 

 observer will see stages of germination. If conditions 

 are not favorable, the spore may withhold germination 

 for considerable time without hurt. Some other spores 

 will not germinate even under the most favorable 

 conditions until after a period of rest. 



Among the fresh water algae, many of which flourish 

 in ponds that are liable to be dried up in late summer and 

 frozen up in the winter, resting spores often enable the 

 species to survive these conditions. Drouth would kill 

 the parent plants or the more delicate kinds of spores. 

 Freezing would be likely to do the same. The resting 

 spores, often with thick walls, are unhurt. Furthermore, 

 even though the moisture and temperature are right, the 

 food required by the organism may not be present. In 

 such a case germination would be disastrous, because the 

 young germinating plant is very tender. 



We see then that spores reproduce the plant, but they 

 do more than this. Because of their variety in form and 

 in behavior they serve to help adjust the species to some 

 of the unfavorable features in its surroundings and to 

 help it take advantage of the favorable ones. 



