1920] CLAY BERG— UPLAND SOCIETIES 45 



mum canadense Desf., Tiarella cordifolia 



Mitchella rep 



typical 



Walloon 



trifle 



grass 



At Bay View the herbs and shrubs show something of a tendency 

 to segregation into patches dominated by different types. Three 

 quadrats of a square meter each taken here were: (1) Tiarella 92, 

 Streptopus roseus 8, Dentaria 4; (2) Taxus 24, Dentaria 8; (3) 

 Allium 116. 



Variants. — Both xerarch and hydrarch types can be distin- 

 guished. The xerarch occurs on high or hilly ground and is both 

 drier and more open. Either hemlock or beech is prominent. The 

 hydrarch type, shown well behind Bay View, is found in valleys and 

 low ground, either occurring along streams or bearing standing 

 water part of the year. The characteristic trees are linden and 

 yellow birch. The herbage is closed and rich, as many as 40 species 

 being found. Marchantia, Equisetum scirpoides Michx., orchids 

 such as Lister a contiallarioides Torr., Impatiens biflora Walt., Viola 

 canadensis L., Glyceria nervata Trin., Polygala paucifolia Willd., 

 Habenaria spp., and Lycopus spp. are common; but the most 

 typical character is the large number of ferns. Among the more 

 prominent are Adiantum pedatum L., Asplenium angustifolium 

 Michx., A. acrostichoides Sw., A. Filix-femina Bernh., Phegopteris 

 Dryopteris Fee, P. polypodioides Fee, and Aspidium spinulosum Sw. 



Natural clearings. — Natural glades and openings occur 

 throughout the primary forest. The fall of a tree is followed in a 

 month or so by a rank herbage growth (11), not the fire weed- 

 composite type often following lumbering, but largely composed of 

 naturally native forest path and clearing species. Among these, 

 by the second or third year, spring up suckers and seedlings of 

 maple and beech, mixed with certain clearing tree species, which 

 shade out much of the herbage growth in four to six years. In the 

 healing of the forest gap the clearing trees may be prominent at 

 first, but they are gradually replaced by the maple and beech in 

 course of time. Among the clearing trees are Pr units pennsylvanica 

 L., P. Virginian a L., Tilia americana L., Ostrya virginiana Koch, 



