-84- 



These are usually followed by more mesophytic mosses which in time may be 

 entirely crowded out in the competition with herbaceous plants. In the dune 

 region at the head of Lake Michigan we find near the shore what is known as 

 the Cottonwood dune, because the cottonwood, Populus deltoides Marsh., is the 

 first tree to make a successful growth upon the nearly bare sand. As the dune 

 grows older, or as we go further from the lake among the older dunes, we find 

 that the cottonwood has given place to the Jack pine, Pinus Banksiana Lamb. 

 The pine dune is later replaced by an association of red, white, and black oak, the 

 last oak succession being in some places a pure stand of Quercus alba L. As with 

 the higher plants, so in like manner with the mosses, we may trace a succession 

 in these tree habitats. 



In the rock series the first plants are lichens, or, in very moist places, liver- 

 worts, which are then succeeded by pioneer mosses and these in turn by other 

 mosses or herbaceous plants. In the water series, floating mosses may occur 

 in open water, and along the margin, partly submerged, are the same or related 

 species. As the surface mat is formed in the deeper lakes various types of 

 hydrophytic mosses are abundant in the fen (sedges — bulrush — cat-tail) associa- 

 tion. In the shrub and early tree associations new mosses take the place of the 

 pioneers as in the other cases. 



One of the most noticeable facts brought out by the entire study is the 

 great reduction in number of species in the late oak and climax forests, which 

 appears in marked contrast to the conditions found in many regions.^ The 

 forest floor in all the forests under consideration is nearly free from fallen logs; 

 hence, any mosses must compete with herbaceous plants for possession of the 

 ground. In the ravines, logs and stumps are more common, and here we find a 

 somewhat greater abundance of mosses. 



CoRVALLis, Oregon. 



APLOZIA PENDLETONII PEARSON 



Wm. Hy. Pearson 

 Since I wrote my description of the above species^, I have received from Mr. 

 Pendleton several packets of the same species, with a note: "In fruit when 

 collected." I have not been able to find any trace of fruit, which probably 

 disappeared in the process of drying, but there are numerous perianths. What 

 I described in my note as immature, are evidently normal-sized and perfect 

 perianths. Their smallness, only about half the size of the bracts (perianth .75 

 mm. X .5 mm., bracts 1.25 mm. x .5 mm.) by which they are entirely hidden, 

 affords another good character for this remarkable species. The folds are more 



^ Cooper, Wm. S. The Ecological Succession of Mooses on Isle Royale, Lake Superior. 

 Plant World 15: 197-213. 1912. 



^Pearson, Wm. Hy. Aplozia Pendletonii, n. sp. Bryologist 33 : 50-52. (PI. II, including 

 8 figs.) 1920. 



