(326) 



the vegetation which occupies the ground today is not necessarily 

 the same as that which has been there in the past or which will 

 be there in the future, if the area is left undisturbed. Vegetation, 

 or associations of plants, like the individual plants, is subject to 

 the laws of evolution. It progresses from lower and simpler to 

 higher and more complex forms. For example, in Eastern 

 United States, a rock ledge in the open will first become covered 

 with drought-resistant lichens. As the rock weathers, and soil is 

 formed, herbs can establish themselves and enrich the soil with 

 their remains. Then come shrubs, and these are followed by 

 drought-resistant trees. Generally these trees are light-demand- 

 ing species, such as gray birch, juniper, and so forth. Under 

 these trees the more shade-enduring species establish themselves 

 and eventually crowd out the pioneers. The highest type of 

 forest possible in the region is known as the climax forest. Each 

 successive type creates to a certain extent its own environment, 

 and the climax is the richest, and generally the most moist and 

 densest forest which the climate will produce. In drier climates, 

 like the western plain or semi-arid mountains, the climax vegeta- 

 tion is grassland or brush. 



In this particular case we would like to know whether the 

 hemlock or the hardwoods represent the climax forest. The 

 hardwoods are the common growth, and formed a large part of 

 the virgin forests of the region when the earlier settlers arrived. 

 But hemlock is more shade-enduring than any of our hardwoods 

 hereabouts, except for beech and sugar maple, and other things 

 being equal, should be able to crowd out the oaks if there were no 

 fire, cutting, or other disturbance. Theoretically, therefore, 

 from standpoint of shade more especially, the hemlock forest 

 appears to be a higher type than the mixed oaks, and to be the 

 climax. If so, the conditions beneath it, the environment which 

 it makes for itself, should be more favorable than that prevailing 

 under the oak forest. Various authorities consider the hemlock 

 as one of the most important constituents of the climax for this 

 region if forest fires are kept out, although they believe it to be a 

 question whether or not pure hemlock is the climax. 



Environmental Factors and Instruments 



In this study it was not possible to measure all the factors of 

 the environment which we know influence plants. We were 



