474 BOTANICAL GAZETTE [juxe 



species. On surfaces with a more gentle slope, where the moisture 

 supply is somewhat less but still plentiful, this species, either 

 alone or with Anomodon rostratus, forms the second moss stage. 

 Where exposure to evaporation is greater, Anomodon rostratus 

 alone, of the two species, occurs. Under the Taxus is a close moss 

 carpet in which Thuidium delicatulum forms the third moss layer, 

 and the second species is ordinarily Anomodon rostratus, which has 

 smothered the Grimmia except at a very few points. Other species 

 which help to make up this moss carpet often several inches thick 

 are Climacium americanum and Rhodobryum roseum. This seems 

 to be a moist habitat even during very dry periods. Another even 

 better successional series was found on a rock on a more gradual 

 slope, well shaded by deciduous trees of an older ecological associ- 

 ation, and well above the level of the stream. This rock projected 

 out a short distance from the bank, leaving a small space between 

 the rock and the ground below. On this protected lower surface 

 Fissidens crista tus formed a complete covering and in places 

 extended up over the edge of the rock. Growing over this on the 

 upper surface and reaching down over the edge at some points 

 was a thick mat of Anomodon rostratus. Upon the Anomodon 

 was a third stratum of Thuidium delicatulum and a small quantity 

 of Entodon cladorrhizans, in all forming a compact mat of consider- 

 able depth. No traces remained of the typical pioneer mosses. 

 The lichens showed occasionally under the Fissidens. On the 

 Anomodon were patches of a powdery lichen and also of a fruticose 

 species, showing that these may develop on the mesophytic mosses. 

 Climacium and Rhodobryum again formed a small part of the last 

 moss stage. Growing in this carpet of moss were such plants as 

 Pilea pumila, Geranium maculatum, small ferns, and tree seedlings, 

 indicating that the next succession is to be that of the vascular 

 plants. Many such examples of the vertical succession of mosses 

 are to be found throughout this ravine. 



Such a moss carpet has been described by Cooper (2) for the 

 rock surfaces on Isle Royale, and by Braun (i) for the conglomer- 

 ate rocks near Cincinnati, Ohio. 



At the top of the perpendicular cliffs there seems to be no 

 special variation in mosses. Backward from the margin the same 



