LIFE FOKMS OF NONHYGKOPHILE VEGETATION. 415 



linearifolius and the cosmopolitan tropical smut grass (Sporobolns 

 indicus) are common street weeds. 



ADAPTATION TO ENVIRONMENT IN THE NONHYGROFHILE 

 INLAND VEGETATION— LIFE FORMS. 



In the case of the group of formations just described little need be 

 said in regard to adaptions to the environment. We are here dealing 

 with what is, in a certain sense, neutral ground, lying between two 

 different types of formation which have extreme life conditions, the 

 Sand Strand on the one hand and the Hygrophile Forest on the other. 

 Where the transition is toward 11k 1 Sand Strand the vegetation pos- 

 sesses characteristics which have already been detailed under that 

 heading. On the other hand, where conditions approach those pre- 

 vailing in the Hygrophile Forest the plaid covering becomes corre- 

 spondingly modified, and the modifications can be most conveniently 

 discussed in connection with that formation. Generally speaking, 

 in the Wooded Plain conditions of soil and drainage vary greatly 

 within such narrow limits, and most of the characteristic species show 

 themselves to be so little choice in regain I fohabilaf, 1 hat any attempt 

 to discuss epharmonic modifications in the vegetation as a whole 

 would be altogether unprofitable, even were it practicable. Very 

 limited areas could be taken up in detail with a full description in each 

 case of the physical conditions of the environment and the structure 

 of the organisms forming the plant covering. Or, on the other hand, 

 certain species of peculiar interest possessing well-marked epharmonic 

 characters, e. g. , Senecio tomentosits, Ascynmi stans, could be described 

 at length. But neither mode of treatment would give a satisfactory 

 idea of the ecology of the formation as a whole. It is more expedient 

 to emphasize the heterogeneity of the formations of the Wooded Plain 

 and to point out that the characteristics of the more xerophilous por- 

 tions are similar to those already discussed under the heading of 

 "Sand Strand," while the moist, low-lying areas exhibit the features 

 which distinguish the forested swamps, to be described later on. It 

 may be said, in a broad way, that the general aspect of the vegetation 

 indicates exposure to a considerable degree of heat and light. These 

 influences are largely counteracted, however, by the presence of 

 abundant moisture in the air and soil, the absorption of water by 

 the roots of plants being unhindered by the presence of any consid- 

 erable quantity of sodium chloride, as in the maritime formations, or 

 by that poverty of the soil in oxygen which distinguishes the swamps. 



The nonpalust rine forest, as well as 1 lie drier port ions of the wooded 

 swamps, are exposed to forest fires, which occur at frequent inter- 

 vals, espeeiall}* in the autumn, and often sweep over considerable 

 areas. However, the absence of a marked period of drought pre vents 

 this being an important factor in the life of plants, as is the case in 

 other regions. No modifications of the plants that could be attributed 



