181 



eastern United States. During the ten years that have elapsed 

 since the chestnut disease was first recorded in this country — 

 at New York- — it has spread with amazing rapidity. At the 

 present writing practically all the chestnut in southwestern 

 Connecticut has been wiped out, and there is no part of the state 

 which has been immune from its depredations. In the vicinity 

 of New Haven much of the chestnut has already been exterminated 

 and it is difficult to find a group of treeS; some of which have not 

 been affected by the ravages of the blight. And whether, as 

 some workers think, the blight fungus is a native species, "which, 

 because of peculiar conditions detrimental to the host, has 

 assumed unusual virulence and widespread prominence,"* or, 

 as others maintain, is an invader from the Old World, certain it 

 is that from the present outlook it is destined to have a profound 

 effect on the nature of the climax forest in the eastern United 

 States. 



The influence of man on succession is almost invariably retro- 

 gressive. Man destroys the more ultimate societies and causes 

 them to be replaced by more primitive ones. The cutting of the 

 forest, the introduction of grazing animals, and fire — all of these 

 interfere with the mesotrophic trend of succession. Thus in a 

 recently cleared area mesophytic herbaceous plants are largely 

 superseded by the so-called " fire-weeds ", e. g., Epilobium angus- 

 tifolium, Erechtites hiemcifolia, Erigeron canadensis, Phytolacca 

 decandra, and Verhascum Thapsus; while Betula poptdifolia, 

 Myrica asplenifolia, Populus grandidentata, Popidus tremidoides, 

 Prunus virginiana, Ruhus allegheniensis, Riibus idaeus var. acu^ 

 leatissimus, and other woody plants not represented in the ante- 

 cedent forest may be abundant here. Fire, perhaps, should be 

 considered a natural agency, but as a rule its frequency becomes 

 much greater with the advent of man into a region. 



There is one other phase of succession on trap to which, as yet, / 

 no reference has been made, viz. succession on talus slopes. This 

 is of peculiar interest because it differs in certain respects from 

 the type described above. Taken as a whole the trap ranges extend 

 from north to south. As a rule the hills dip gently toward the 



* Clinton, G. P. Chestnut bark disease. Report Conn. Agr. Exp. Sta. 1912: 

 359-453- pl- 21-28. 1914. 



