1920] TAYLOR— SUCCESSION OF MOSSES 485 



start under the shade of the trees and shrubs. North of the Mineral 

 Springs bog is a low, flat, sandy plain covered with shrubs and marsh 

 grass. The undergrowth is a compact mass of Sphagnum. In 

 many old lagoons which have reached the shrub stage or which have 

 a rank growth of swamp grasses, Sphagnum is growing in rather 

 dense shade, but whether it originated in shade or sunlight cannot 

 now be determined. Another case which is similar to that of 

 Mineral Springs is the presence of 5. subsecundum in isolated 

 patches in the depressions of the Thornton swamp. There is no 

 connection whatever with outside Sphagnum areas. In fact, no 

 Sphagnum has thus far been discovered in the open regions around 

 the swamp. Many of these patches are in the interior of the 

 forest, and all are well shaded during the summer. It is quite 

 true that in both the Mineral Springs bog and the Thornton swamp 

 the trees are bare of foliage during the winter season, and there- 

 fore sunlight will reach the ground during the early spring. This 

 argument, however, can be applied equally to the sedge association, 

 where there is little shade from the coarse sedges until the new 

 growth has begun. In this region, therefore, it appears that 

 Sphagnum must be able to germinate under shade, and that it 

 may be present in forests without having reached these habitats 

 by vegetative encroachment from outside areas. This conclusion 

 is borne out by work done upon the germination of Sphagnum by 

 George L. Bryan. The results of the study have not yet been 

 published, and I am indebted to the kindness of W. J. G. Land of 

 the Botanical Department of the University of Chicago, under 

 whose direction the work was carried on, for permission to refer 

 to the results. Bryan made many careful experiments upon the 

 germination of Sphagnum spores under various conditions of soils 

 and sunlight, and found that germination occurred in all degrees 

 of sunlight and in darkness itself. Apparently there is some other 

 determining factor which controls the presence of this group of 

 mosses. 



The tamaracks form a border about the bog. On the outer 

 margin they are being displaced by other bog trees, as Betula 

 lutea and Nyssa sylvatica. The tamaracks grow on hummocks, while 

 the depressions between them may be very wet or even filled with 



