﻿2o6 BOTANICAL GAZETTE [march 



cauloii paschale. The more shaded basal half of the talus is so 

 covered with these plants that a casual observer would scarcely 

 notice the smaller and less numerous plants of the community. 

 Yet a little closer observation brought to light a few ferns, quite 

 a sprinkling of mosses, a half-dozen species of smaller Cladonias, 

 and a few species of the foliose Nephroma, Peltigera, Parmelia, 

 and Umbilicaria. On account of the less shaded conditions 

 toward the upper part of this southward exposed talus, the 

 Cladonias characteristic of the society are there less numerous 

 and give way in part to the above-named foliose lichens and a 

 number of species of the crustose Lecanora, Biatora, Buellia, and 

 Lecidea. The talus sloping to the south is not, as hinted above, 

 well shaded toward the upper part where the limbs of the large 

 trees growing upon the lower part do not overhang. Of course 

 the trees above a talus with south exposure do not furnish any 

 considerable amount of shade. Consequently, rock decay has 

 not gone on so rapidly toward the top of the talus, and neither 

 this condition nor the lack of shade has been so favorable for 

 the development of the erect-growing Cladonias. Hence there 

 are present a large proportion of the crustose lichens upon the 

 upper portion of the talus, these plants, in their closely adnate 

 position upon the rocks, being better adapted to the more 

 exposed portion of the talus because they easily hold the mois- 

 ture between their lower surfaces and the rocky substratum and 

 also readily absorb moisture from the rocks. The size of the trees 

 would indicate that this talus is older than the one first consid- 

 ered and about two miles distant, and whether this is true or 

 not, there is every indication that a fire ran over the one at 

 Howenstine Bluff at no very distant day and killed the plant life 

 of the spot so that the present growth is comparatively recent. 

 The presence of a good sprinkling of old woody debris upon the 

 talus now under consideration {^jig. 5) shows that this condition 

 alone does not indicate the presence of a Cladonia society com- 

 posed of the smaller species. In this instance doubtless the 

 Cladofiia rangiferina society has succeeded the Cladonia gracilis 

 community as the trees became larger, furnishing more ombro- 

 phytic conditions, and as the poplars and other deciduous trees 



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