154 J. '^- CRIBBS 



proportionate increase in the representation of deciduous species 

 until they entirely replace the former. This mixed type of 

 forest commonly extends from a point about 100 feet above the 

 bottom of the slope to a height of 250 feet or even as much as 

 450 feet. The lower border is determined by the entrance of 

 Acer ruhrum and Fagus, both trees of distinctly mesophytic char- 

 acter. Magnolia gains an entrance slightly higher on the slopes 

 and is soon followed by Quercus rubra. Betula lenta commonly 

 extends throughout the mixed forest stage, occurring most 

 abundantly in wet depressions and the numerous small ravines. 

 An essential fact that should not be overlooked is, that the decidu- 

 ous members of this stage are our most mesophytic trees, and 

 species which occur as regular components in the climax decidu- 

 ous forest of the moraines. 



The disposition of the undergrowth when considered from the 

 lower to the upper portions of this stage, also shows transitional 

 features. In the deep shade of the pine-hemlock-beech-maple 

 stage it is closely similar to that accompanying the evergreen 

 formation on the lower slopes, being low and dominantly ever- 

 green; but as the deciduous members become more prominent 

 the lower stratum likewise undergoes a change. Lycopodium, 

 Clintonia, and Viburnum, are gradually replaced by different 

 species; the latter two by other species of the same genus, namely, 

 Clintonia umbellatula, and Viburnum acerifolium. Numerous 

 new species are added to the flora and include Actcea alba, 

 Geranium maculatum, Lycopodium obscurum, Polygola pauci- 

 flora, Sambucus racemosa, Streptopus aureus, Lonicera americana, 

 Trillium undidatum, Viola pubescens, etc. 



Tree seedlings constitute most of the woody undergrowth, 

 so that in addition to the shrubby species already cited, Kalmia 

 latifolia, Smilax hispida, and Rhododendron maximum are the 

 only forms of frequent occurrence. Seedlings of Fagus, Acer, 

 Magnolia, Tsuga, and Betula, are conspicuous throughout this 

 zone, but those of Pinus Strobus are relatively scarce. 



