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THE POPULAR SCIENCE MONTHLY. 



tnmi hygroinetricum^ a kind of fungus which grows underground, 

 the outer envelope which is hard, tough, and hygrometric divides, 

 when mature, in strips from the crown to the base ; these strips spread 

 horizontally, raising the plant above its former position in the ground ; 

 on rain or damp weather supervening the strips return to their former 



Fig. 1. Valisneria spiralis, a, female flower ; h, male flower ; c, floating pollen. 



position ; on the return of the drought this process is repeated, until 

 the fungus reaches the surface and spreads out there ; then the mem- 

 brane of the conceptacle opens and emits the spores in the form of 

 dust. 



I have already referred to the case of the common dandelion. 

 Here the flower-stalk stands more or less upright while the flower is 

 expanded, a period which generally lasts for three or four days. It 

 then lowers itself, and lies more or less horizontally and concealed 

 during the time the seeds are maturing, which in our summers occupies 

 about twelve days. It then again rises, and, becoming almost erect, 

 facilitates the dispersion of the seeds, or, speaking botanically, the 

 fruits, by the wind. Some plants, as we shall see, even sow their 

 seeds in the ground, but these cases will be referred to later on. 



