DISTRIBUTION OF SPORES AND SEEDS. 353 



movements, brought about by variations in light and tem- 

 perature, which act as stimuli. (See ^| 286.) 



II. Adaptation to distribution of spores. 



The fact that spores are found in every group of plants 

 from the lowest to the highest makes it probable that a great 



Fig. 396. Fig. 397. 



Fig. 396.—^, flower of California poppy (Eschscholtzia), opened in sunshine; B, the 



same, closed in wet weather. Natural size. -After Kerner. 

 Fig. 397.—^ , aerial hypha of Pilobolus crystallinus, with sporangium. The hypha is 



swollen beneath the sporangium and very turgid. B, the same with sporangium torn 



off at base and being shot away by the violent escape of the mucilaginous contents of 



the hypha. Magnified about 10 diam.— After Kerner. 



variety of ways will have been adopted by plants to secure 

 their distribution. The more important ways may be grouped 

 as follows : 



478. 1. By turgor and tension. — Among the fungi, spores 

 are often projected from the spore case by the pressure upon 



