436 proceedings: botanical society 



excess of all others. No arborescent representatives of the monocot- 

 yledons are found growing naturally within the District. The oaks 

 are the most prominent among the broad leaved trees of the District 

 and constitute from one-half to three-fourths of the upland forest 

 cover. They consist largely of black, red, and white oak. The most 

 prominent conifer of this region is Pinus virginiana. Two naturalized 

 trees of the District deserving special mention are the Japanese paper 

 mulberry and the Ailanthus or Tree of Heaven. Both were introduced 

 from China and Japan and are the most thoroughly established of the 

 exotic trees. 



Mr. Frederick V. Coville discussed Humus as a factor in plant 

 distribution. Mr. Coville exhibited two samples of organic matter, 

 the one, brown, only partially decomposed remains of the leaves and 

 roots of laurel and oak, which make up a large proportion of the 

 acid humus of this section; the other a black, fully -reduced, nonstruc- 

 tural leaf mold, the reduction in this case being favored by the large 

 amount of calcium contained in the leaves from which the mold is 

 formed. The lime content of the sample of leaf mold shown was six 

 per cent, expressed as calcium oxide. Mr. Coville discussed the effect 

 of these two types of organic matter on the distribution of plants. 



Mr. P. L. Ricker discussed Collecting and preparing specimens. 

 Mr. Ricker called attention briefly to the older methods of collecting 

 and drying plants and suggested the advisability of using corrugated 

 driers as well as neat portfolios, especially for field work. Where 

 corrugated driers are used the plants can be dried without change of 

 blotters but, in case of rainy weather, the use of artificial heat is recom- 

 mended. 



Following this the various papers were discussed informally by the 

 members on the program and by Messrs. Safford, Beattie, Norton. 

 Waite, Lewton, and Shantz. 



H. L. Shantz, Corresponding Secretari/. 



