BOTANICAL SURVEY— SUGAR GROVE REGION 289 



and it has a southeast exposure, so that it receives sunlight till nearly 

 noon. The sand which covers the floor is perfectly air-dry, very fine, 

 and dusty enough to be unpleasant. It is totally barren except where 

 water drips down from above or oozes out from the crevices of the rock, 

 and is really a small patch of desert in the midst of luxuriant meso- 

 phytic habitats. Similar conditions are presented by many other caves 

 of all sizes, down to mere ledges. In many of them, as in Old Man's 

 Cave, the floor is considerably above the general level of the bottoms of 

 the ravines in which they occur. In others the floor of the cave is con- 

 tinuous with the talus slope at the base of the cliff, in which case, if 

 the conditions are not too severe, the flora is nearly allied to that of 

 the talus slopes in general. (See p. 281.) 



Verhascum Thapsus is perhaps the most characteristic plant of the 

 dry caves, being nearly always found there. By reason of its very long, 

 slender roots, which extend far and wide through the loose sand, and 

 the protective hairy investment of the leaves, it is able to endure more 

 severe conditions than any other plant whose seed reaches these places. 



Muhlenlergia diffusa is another practically constant inhabitant of 

 the dry caves, forming circles around the points where water drips 

 from the roof, from which it reaches out radially as far as the water 

 supply will permit, its development varying therefore from season 

 to season. 



The high bush blackberry (Ruhus aUegheniensis) likewise always 

 occurs in such caves, thereby exhibiting an amount of endurance of 

 xerophytic conditions which was surprising to the writer in view of 

 its general habitat. But it is plainly evident that the conditions are 

 too severe for its best development, as its canes are frequently killed 

 back and never develop as robustly as in ])asture lands. It flow(>rs and 

 fruits freely, however. 



In Old Man's Cave a conspicuous place is taken by the angelica 

 tree, Aralia spinosa, altho this cannot be said to be a general inhab- 

 itant of the caves, since it is rare north of Queer Creek. 



Wet Caves. When the caves are moist and at the same time well 

 illuminated, their flora differs but little from that of the forest floor. 

 Wluni, however, a cave is dark, all other conditions being favorable, tlu^ 

 vegetation becomes arranged in something like a zojial series, according 

 to the minimum light requirements of the constitiHiit species, each of 



