An Ecological Study of Buckeye Lake. 57 



tion deficiency of the air of the open bog as compared with the 

 thicket. Out in the open the fronds are small and stunted and held 

 rigidly erect with pinnules folded and pinnae pressed against the 

 rachis. (Fig. 20). In the margins of the shrub zone, the tall 

 spreading fronds attain their maximum growth with pinnae and 

 pinnules expanded to their fullest extent. (Fig. 21). All the 

 plants of the bog-meadow show adaptation or adjustment to the 

 more xerophytic habitat ; blit the ferns offer the most striking 

 example. Peltandra virginica, a marsh plant, occupies small pools 

 in the central bog. These pools at normal water level are nearly 

 full of water, the walls are closely covered with Sphagnum which 

 grows down to or even below the water. On such moist banks as 

 these Viola blanda is enabled to invade the bog. In the fall 

 when the water is low, the pools are almost free from standing 

 water and contain the dead decaying Peltandra leaves and the 

 large fruit clusters. In one such depression on the west side of 

 the meadow are thrifty Nymphaea advena plants. (Fig. 25). 



V. The Gaylussacia heath or low shrub association. 



The heath association is of the low shrub character of 

 vegetation. In a typical bog the characteristic plants of this as- 

 sociation are low shrubs of the Ericaceae and Vacciniaceae fam- 

 ilies as Gaylussacia resinosa, Andromeda polifolia, Chamaeda- 

 phne calyculata. Ledum groenlandicum and Potentilla fruticosa, 

 of the Rosaceae associated with Sphagnum sp. and often with 

 Rubus hispidus as a ground cover. These form a dense, compact, 

 almost impassable stratum. This association is almost wanting in 

 Cranberry Island. There are a few small clumps of Gaylussacia 

 resinosa, which are with two exceptions just at the inner mar- 

 gin of the shrub zone or entirely within this zone. (Fig. 22.) 

 The two exceptions are two small groups of Gaylussacia in the 

 open meadow (Fig. 13 V). The shrubs are stunted and did not 

 blossom in 1910. They have blossomed freely during the spring 

 of 191 1. The heath is spreading quite rapidly but is still mostly 

 confined to the shrub zone. The association is composed of but 

 one society, the Gaylussacia society, in which are no other species 

 of the heath association ; but Sphagnum cymbif olium, S. acuti- 



