304 



ECOLOG 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 



