VARIATIONS OF THE INLAND MIXED FOREST. 403 



polypodioides (incanum). The last is common, however, only in the 

 recesses of the Dismal Swamp. 



The aspect of the inland forest, where? its primitive condition has 

 been preserved, is usually that of a more or less compact assemblage 

 of woody plants, forming, in typical examples, a series of three 

 layers — the first of undershrubs, the second of tall shrubs and young 

 trees, and the third of fully developed trees. Lianas may, as we have 

 seen, enter copiously into any one or all of the layers, according to 

 conditions which vary within short distances. More than three well- 

 defined and approximately coordinate layers are rarely to be distin- 

 guished in the nonpalustrine forest formation; for, wherever herba- 

 ceous phanerogams, or mosses, or saprophytic fungi are present in 

 considerable numbers, the layer of undershrubs, and often that of 

 high shrubs, is correspondingly reduced. 



As has already been pointed out, conditions of soil, especially of 

 soil moisture, are often very different in the nonpalustrine forest, at 

 points only a slight distance apart. A few steps serve to take us from 

 a spot where the soil is dry, sandy, and almost devoid of Immus to 

 one where it is moist, contains a high percentage of silt, and is well 

 stocked with humus. Every such difference of soil is accompanied 

 by a corresponding change in the character of the vegetation. But, 

 owing to the wide range of adaptability to difference in soil which is 

 exhibited by most of the important woody plants of this formation, 

 and the insensible gradations from the driest and lightest to the 

 wettest and heaviest soils, it is not practicable to distinguish associ- 

 ations which have a general distribution in the region, and can be 

 recognized as such at different points, although more extended study 

 may render possible such segregation. Nevertheless, it is important 

 that we should have a more exact conception of the physiognomy and 

 constitution of the formation, and for this reason a number of limited 

 tracts of the nonhygrophile forest, lying as far apart as possible in 

 space and in character, will be described at some length. In each 

 case the elements of the description were jotted down in a notebook 

 on the spot, and it should therefore afford an accurate picture of 

 actual conditions. 



While there is much that the several examples have in common, as 

 should be the case in the parts of a single formation, there are also 

 more or less important distinguishing characters. Thus, in one spot 

 Pifius taeda is almost the only tree, while in another deciduous 

 species strongly predominate. Here young plants of Liquidambar 

 form the principal undergrowth, there it is composed largely of Myrica 

 or of different oaks. Lianas are abundant in one bit of woodland, 

 while quite unimportant in another. Herbaceous plants may find 

 plenty of space for development in a tract of open forest, while only 

 a few meters distant they are crowded out by a dense growth of under- 

 shrubs. None of the following cases can be taken as a type of the 



