274 CLARENCE F. KORSTIAN 



tilla thurberi, Hypericum formosum, Lobelia gruina, Agrimonia 

 brittoniana var. occidentalis, Gaura suffulta, and Tagetes lemmoni. 



Weaver 12 has recorded the variation in the vegetative under- 

 growth with a change of the site in the cedar (Thuja plicdta) 

 forest on the Thatuna Hills in southeastern Washington. Near 

 the streams the forest floor is covered with Athyrium cyclosorum 

 which gives way farther back to a rather dense growth of Rubus 

 parviflorus, Vagnera amplexicaulis, Tiarella unifoliata, Trillium 

 ovatum, Clintonia uniflora, Disporum ma jus, Pyrola sp., Actaea 

 spicata arguta, and Coplis occidentalis, Viola sp., Streptopus 

 amplexifolius, and Phegopteris dryopteris. These together with 

 the cedar seedlings comprise the characteristic undergrowth, 

 while farther up the slope there is almost no living ground cover. 



Fuller 13 notes the relation between the mesophytism of a site 

 and the undergrowth in some comparatively undisturbed beech- 

 maple forests about 45 miles southeast of Chicago, when he 

 states that the lower evaporation in the ravine may be a suffi- 

 cient explanation for the presence upon its slopes of a much 

 greater abundance of such delicate forms as Dicentra canadensis, 

 D. cucullaria, Impatiens biflora, and Asplenium angustifolium. 



Peters, 14 as a result of observations made in Northampton 

 County, Pennsylvania as early as 1806, calls attention to the 

 fact that the timber alone is not always an invariable indicator 

 of the capabilities of the land. Hemlock (Tsuga canadensis), 

 white pine (Pinus . strobus) , and pitch pine (Pinus rigida) were 

 reported as occurring on deep, fertile loams as well as on the 

 thinnest, sterile, sandy soils. It is readily seen that the vege- 

 tation must be properly correlated with its habitat and the 



12 Weaver, John E. Evaporation and Plant Succession in Southeastern Wash- 

 ington and Adjacent Idaho. The Plant World 17: 273-294. 1914. 



13 Fuller, George D. Evaporation and the Stratification of Vegetation. Bot. 

 Gaz. 54: 424-426. 1912. 



14 Peters, Richard. The Departure of Southern Pine Timber and Proof of 

 the Tendency in Nature to a Change in Products on the Same Soil. Memoirs of 

 the Philadelphia Society for Promoting Agriculture, containing communica- 

 tions on various subjects in husbandry, and rural affairs, Vol. I, page 30, Phila- 

 delphia. 1815. From notes on plant succession abstracted and furnished by 

 Dr. H. L. Shantz. 



