XL] STONEWORTS, AND PEPPERWORTS. 165 



liar hygrometric properties. If placed upon a glass- 

 slide, breathed upon, and then placed under the 

 microscope, these .elaters will be seen to undergo 

 some curious movements. " Some will be quite 

 closed up, the elaters being so closely applied to the 

 spores as to be scarcely distinguishable; others, again, 

 will be seen gradually unfolding the filaments, and a 

 few may be observed to move with a sudden start, as 

 it were, from the contracted state of the elaters to 

 that of full expansion. -The ultimate cause of this 

 movement is quite unknown. That it depends upon 

 the amount of moisture with which the spores are 

 surrounded there can be no doubt Most probably 

 it takes place by the contraction and expansion of 

 the cells of which the elaters are composed, under the 

 varying influence of the moisture contained in the air. 

 The phenomenon is a very curious one, and should 

 by all means be seen by every one who possesses a 

 microscope" (H. W. S. in "Science Gossip," 1878). 



FIG. 117. 



FIG. 119. 



The spore on germinating gives rise to a prothallus 

 similar to that of ferns, and in the same manner 

 bears antheridia and arcJiegonia, which ultimately 

 develop a true bud, and from this the new plant 

 springs. 



