308 BOTANICAL GAZETTE | MAY 
the next rain they are as fresh as ever. Nitrogen compounds 
are obtained from the rain water or from particles of dust which 
lodge around them and other requisite inorganic compounds come 
from the rocks. Thus these pioneers of vegetation, as has been 

Fic. 4.—A maple-beech-hemlock forest in sandy soil 6n North Manitou island. 
he diene consists principally of maple, beech, and helmlock seedlings and 
young trees; also Taxus Canadensis and Mitchella repens. The young trees indicate 
that the next generation of trees will be the same as the presen 
shown by various writers, are able to flourish in the most 
xerophytic situations. They not only aid in disintegrating the 
rocks, but by decay furnish humus constituents to the soil, and 
in these ways, pari passu, both organic and inorganic soil is 
made. : 

