l6 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. 



brought by glacial or water agency from a greater or less dis- 

 tance, may be and often is entirely different in chemical compo- 

 sition from the underlying rock. Hence within a small area a 

 variety of soils may be found, while on the other hand soils 

 essentially similar to each other may overlie very different bed- 

 rock formations. 



Other influences have an important bearing in this connec- 

 tion. Topographic features correlated with the amount of 

 moisture in the soil and degrees of light and shade affect plant 

 distribution in a marked degree. Thus, the sand plains, the cedar 

 swamps, the trap rock and other precipices and the larger river 

 valleys have their characteristic plants. 



There is another small group of species chiefly confined to the 

 southeastern part of the state which belongs to the flora of the 

 Atlantic Coast Plain of the middle and southern states. In the 

 case of these plants, as in that of certain northern plants found 

 within our borders at isolated stations far outside their usual 

 range, it is probable that they represent the shrunken remnants of 

 far larger colonies which grew there in earlier times and under 

 more favorable climatic conditions. 



Another agency profoundly influencing the distribution of 

 plants is the fierce unceasing struggle for existence between the 

 various species. 



Only a beginning has been made in working out these 

 problems of ecology in their application to our Connecticut flora. 

 They offer a fresh and inviting field for careful research, and it 

 is to be hoped that many observers may soon be interested to 

 undertake the task of supplying the deficiencies of our knowledge 

 in this direction. 



