Periodical Literature 39 



cent. The ratio of between 80 and 100 per cent, seems incident 

 with the occurrence of ' ' oak openings " , " open forest ' ' and 

 "groves" on the uplands and dense forests on the low lands. 



In the article, here briefed, the idea is followed up and a 

 further differentiation of forest centers made. 



By center is understood a locality in which the complex of 

 climatic factors is most favorable to the development of a certain 

 type of vegetation, conditions for this type becoming more and 

 more unfavorable with the distance from the center. It is not 

 implied that plants have necessarily spread from these centers. 



The St. I^awrence basin is suggested as the center of a unique 

 type of forest, ecologically and climatically distinct, the North- 

 eastern conifer center with Pinus strobus, Picea mariana, Tsuga 

 canadensis, Abies balsamea, Pinus divaricata, Larix laricina 

 forming the "climax" forest type, while the lower Ohio basin 

 and Piedmont plateau is the center of the " climax ". Deciduous 

 forest center, with Quercus alba and rubra, Hicoria alba, Acer 

 saccharum, Fagus americana, Fraxinus america7ia, Liriode7idron 

 tulipifera and Magnolia acuminata in best development. The 

 term climax forest is used by ecologists to designate the forest 

 type which as a result of evolutionary changes is the final type 

 of a given locality. 



With these conceptions of geographic centers for instance in 

 Michigan the belt of maple-beech forest appears as ' ' the attenu- 

 ated border of the climax stage of the Southeastern Deciduous 

 forest center. ' ' Similarly in the mountain region of the Southern 

 Appalachians the Southeastern conifer forest, centering in the 

 South Atlantic and Gulf coastal plain, the Northeastern conifer 

 forest and the Deciduous forest center touch, and (we sug- 

 gest) here on the meeting ground edaphic factors must become 

 superior to climatic in giving preference to the one or the other 

 formation. 



If these conceptions are tenable, and, with proper reservations 

 as to the influence of edaphic factors, the reviewer thinks they 

 are, not only clearer ideas regarding forest-types and forest dis- 

 tribution must result, but practical application of the new knowl- 

 edge to silviculture will suggest itself readily to foresters. 



Forest Centers in Eastern America. American Naturalist. Dec, 1905 

 pp. 875-889. 



