304 



ECO LOG Y. 



and other low-growing plants often cover and protect the soil 

 from the direct rays of the sun, and thus conserve moisture. 



Fig- 255- 



Self-sown white pine in abandoned orchard ; trees 9-20 years old. Near Ithaca. (Photo- 

 graph by the author.) 



The clovers which spring up here and there, by the aid of the 

 minute organisms in their roots, gather nitrogen. The meli- 

 lotus, the passion flower, and other deep-rooted plants reach 

 down to virgin soil and lift up plant food. Each year plant 



