No. 11.] THE BRYOPHYTES OF CONNECTICUT. 31 
In treating an area such as the continent of North America, 
where all gradations from an arctic to a tropical climate are 
encountered, the first of these factors bears an important’ 
relationship to the character of the vegetation. Many Bryo- 
phytes are exclusively northern in their range, while others 
are restricted to tropical regions. A comparatively small 
number are found from the arctic regions to the equator. In 
considering the Mosses and Hepatics of Connecticut, however, 
latitude is of relatively little importance. 
In the same way the second factor may be disregarded, 
since nowhere in the state are the differences in altitude suf- 
ficient to produce any appreciable climatic effect. 
To a certain extent the nature of the substratum determines 
the character of the bryophytic flora, and various societies 
might be defined from this point of view, as, for example, the 
following: —.species growing on rocks; species growing on 
soil; species growing on living trees; species growing on dead 
trees, rotten wood, etc. Yet the boundaries between such 
societies are often vague, since many species flourish equally 
well on a variety of substrata. 
Except in the northwestern part of Connecticut, it is prob- 
able that the actual chemical composition of the rocks and soil 
has very little direct effect upon the character of the vegeta- 
tion. Indirectly, however, the structure of the underlying 
rocks is an important factor, as may be seen by considering 
the geography of the state. 
“The state of Connecticut is naturally divided into three 
areas, the Eastern Highland, the Western Highland, and the 
Central Lowland. The Central Lowland may be further 
divided into a central range of hills and an eastern and a 
western valley.”* The sedimentaries in the valleys with the 
overlying drift tend to produce a more or less level surface, 
which is interrupted only by a few ravines and by occasional 
bogs. For the most part this area is under cultivation, but, 
although favorable for agriculture, it does not present condi- 
tions conducive to an extensive bryophytic flora. In marked 
contrast to this uniform area are the trap ridges which ‘rise 
*Rice and Gregory: Manual of the Geology of Connecticut. Conn, Geol, & 
Nat. Hist. Surv., Bull. 6, p. 17. 1906. a 
