240 Nichols: The vegetation of Connecticut 



Marsupella emarginata Didymodon ruhellus 



Plagiochila asplenioides Anoectangium Moiigeotii 



Scapania nemorosa Plagiopus Oederi 



Radula complanata Plagiothecium denticulatum 



Lejeunea cavifolia Hylocomium hrevirostre 



Hymenostylium curvirostre Thamnmm alleghaniense 

 Inhabiting the drier dififs, either in crevices or on the rock 

 face, are such forms as: 



Metzgeria conjiigata Ulota americana 



Cephaloziella Hampeana Bartramia pomifortnis 



Porella platyphylloidea Hedwigia albicans 



Leucolejeunea clypeata Neckera pennata 



Frullania Asagrayana Haplohymenium triste 



Rhabdoweisia denticulata Anomodon atteniiatus 



Grimmia conferfa Anomodon rostratus 



The Influence of the Chemical Nature of Rocks on the Dis- 

 tribution of Bryophytes. — In earUer papers of this series* brief 

 reference has been made to the influence of the chemical composi- 

 tion of the substratum on vegetation. In glaciated regions like 

 Connecticut, where most soils are transported and residual soils 

 are rare, this influence is nowhere seen to better advantage than 

 in ravines and similar localities where there are exposures of bare 

 rock. In Connecticut, the problem as to the effect of the chemical 

 nature of the substratum on vegetation concerns chiefly calcareous 

 versus potassic rocks. The granites, gneisses, schists and sand- 

 stones, which comprise the bed rock over much of this state, are 

 for the most part rich in potassium, which is one of the principal 

 constituents of orthoclase feldspar and of mica (muscovite and 

 biotite). Calcium also, as one of the components of plagioclase 

 feldspar, hornblende, and certain other minerals, is present in 

 some of these rocks, and in the sedimentary formations — the sand- 

 stones and shales — -small amounts of calcium carbonate may be 

 included in the cementing material. But, except locally, the 

 amount of lime in these rocks, in so far as it affects vegetation, 

 appears relatively insignificant. The important lime-bearing for- 

 mations of Connecticut are trap and marble. The former contains 

 potassium in small amount, one or two per cent.; the latter con- 



* See Torreya 13: 109,110. 1913; 14: 185. 1914. 



