I. Studies of the Life History, Habits, and Taxonomic Relations of a New Species of Oberea (Oberea Ulmicola Chittenden) (Volume 7, nos. 1-10 ); Ii. ... of Neocerata Rhodophaga Coquillett

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1910. Excerpt: ... those forces or conditions which have or have had direct influence, and among them may be mentioned the historical factors of migration, succession, and the like; the physical factors of water, temperature,and soil; and the biotic factors, including competition, layering, and others. The various factors are by no means independent, but each influences the others and is to some degree influenced by them. The biotic and historical factors are here mentioned either incidentally or under thehead, ingof phytogeography, but the physical factors are in many cases so different from those normal to other parts of Illinois that they are discussed more in detail. The physical factors which aid in the control of the vegetation of any area have been divided by Schimper ('98, p. 174) into two groups, climatic and edaphic. The climatic factors are temperature and rainfall, and they determine respectively the specific composition of the flora and the general character of the vegetation, whether forest, prairie, or desert. Similar climatic factors are operative over broad areas, and the changes from one type of climate to another are usually very gradual. Local variations in the vegetation are due to the physical or chemical composition of the soil, to its exposure to the sun, to the available supply of water, and to other such factors, designated collectively by the term edaphic. Edaphic factors are always influenced by, and are sometimes the direct result of, the climate. They are also modified to a greater or less extent by the plant-covering, as will be shown later in the discussion of the plant associations. Although the climate of the Illinois River valley sand region is in every essential respect like that of other parts of central and western Illinois, a strikingl...