88 coville: formation of leafmold 



they live. Unfortunately the work of botanists on these fungi 

 has been confined largely to the determination of the mere ana- 

 tomical fact of their occurrence on the roots or in certain of the 

 root cells, with descriptions of their size and configuration. Little 

 attention has been paid to the isolation of the fungi, their culture 

 and identification, or to the demonstration of their physiological 

 action. The only hypothesis, however, that satisfactorily ex- 

 plains what we already know about the mycorhizal fungi is that 

 they prevent the nitrogen starvation of peat-inhabiting plants. 

 It is well known that certain peat-bog plants, as for example 

 sundew, trap insects, digest them, and assimilate their nitrogen. 

 It is to be hoped that within a few years we shall be equally well 

 informed about the function of the mycorhizal fungi. But even 

 now we may speak of their probable function with confidence. 



The mycorhizal fungi are known to occur on most of the trees 

 that inhabit acid situations, for example chestnut, beech, oaks, 

 and conifers. The ordinary hillside pasture in New England is 

 a mycorhizal cosmos. The clubmosses have them, the sweet 

 fern, the blueberries, the ferns, the orchids. In our sandy pine 

 and oak woods about Washington almost all the vegetation 

 possesses mycorhizal fungi. One comes to think of the giant 

 oaks as dependent on these minute organisms. 



Were Solomon to write a new edition of the Proverbs today I 

 am sure that he would tell us ' ' There be four things which are 

 little upon the earth, but they are exceeding strong," and that 

 among the four he would include ''The little brothers of the forest, 

 they seek not the light but the leafy earth; they prepare for the 

 oak the strength that is his." 



Our American agriculture, derived in the main from the agri- 

 culture of the Mediterranean region, and that in turn from the 

 older agriculture of Persia, is chiefly made up of plants that 

 thrive best in alkaline or neutral soils. Altho many of our soils 

 in the eastern United States are naturally acid we try with only 

 indifferent success to grow in them these alkaline plants of south- 

 ern Europe and the East. Altho some of our agricultural plants 

 are tolerant of acidity, our agriculturists have not yet recognized 

 the possibility of building up for acid soils a special agriculture 



