104 



has shown that even in the open shifting sand between the oaks, 

 a very xerophytic situation, such fungi as various species of 

 Geaster and Lycoperdon occur. Plants Hke these can hardly be 

 called xerophytes, but on the contrary are extremely mesophytic, 

 the entire aerial life of the plant being of extremely brief duration. 

 Otherwise the plants probably exist only as spores, the delicate 

 mycelium being unable to withstand any severe or prolonged 

 drought. Of similar habit are many desert plants, both annual 

 and perennial, which spring up during wet seasons and persist in 

 dry periods only underground, or as seeds. These plants, as 

 pointed out by Schimper (3) possess no xerophytic structures, 

 and would, therefore, be called mesophytes. Comparable in 

 habit to these desert perennials, it seems to me, is the Indian 

 pipe, although, unlike them, its activity must be confined to a 

 definite period, on account of seasonal changes in temperature. 

 The question might naturally be raised that if the plant is able 

 to live in xerophytic habitats, it should also be found in the more 

 exposed places, as are the fungi. But the peculiar short root 

 system of this species would be exposed quickly by a shifting of 

 the sand, even though slight, and the plant would necessarih^ 

 perish. As I have stated, the fungi probably exist over severe 

 periods in the form of spores, while the Indian pipe cannot pro- 

 duce fruit in a single season from the seed, in all probability, so 

 that a stable soil is requisite. 



It would seem, however, that the plant is confined to woodland' 

 habitats, whether mesophytic or otherwise. Sunlight, as is well- 

 known, causes a blackening of the stems, and extreme sunlight 

 would doubtless kill them. It is unlikely, therefore, that the 

 plants could exist in the open. But given a degree of shade, it 

 seems reasonable to suppose that they could exist in some of the 

 most xerophytic places. 



The late mid-September blooming, which seems to be the key 

 to the persistence of the plant here, could be accounted for in the 

 following manner. Fuller (4), who investigated the evaporating 

 power of the air in its relation to the vegetation of the sand dunes, 

 has shown that commencing about the first of September there is 

 a decided drop in the rate of evaporation and this drop continues 



