

200 BOTANICAL GAZETTE [march 



there occurs a layer of fine black peat, similar in form to that now 



found in the open lakes. This is the "completely decomposed 



stratum" just mentioned. Fig. 8 shows a microscopical section 



taken 3 ft. from the bottom, and further studies of the figure 



reveal in addition to the usual structureless drift, woody and 



herbaceous plant fragments, pollen, spores, spicules, etc., all of * 



which have been preserved from decay by a perpetual water cover 



and natural acidity. It is manifest that this material does not 



represent the final stage in the reduction of fibrous peat, but rather 



an accumulation of drifted and wind-blown matter which was 



precipitated at some time when lacustrine conditions prevailed. 



This relation is still more obvious when it is demonstrated to be 



similar in the most exacting detail to that already shown to be 



characteristic of present lake deposits and illustrated in figs. 1-4. 



amorphous mass, there appears a light brown 



material 



"saw grass" 



marshes. Fig. 9 shows photomicrographically the true nature of 

 the substance. In addition to root fragments across the illustra- 

 tion, there appears the usual disorganized material, pollen, spores, 

 and spicules, all of which indicate an allocthonous origin. An even 

 clearer idea of the lacustrine nature of this peat may be obtained 

 by reference to fig. 10. In the upper right hand corner of the 

 figure is a much distorted fragment from some herbaceous plant, 

 amorphous matter, and ejecta. The most noticeable, as well as 

 one of the most significant, features, however, is a fern sporangium 

 and a sponge spicule which could not occur in juxtaposition except 

 through sedimentation in open water. 



Microscopical studies of this vertical series indicate that about 

 the time when the last of the herbaceous material had been de- 

 posited, the accumulated mass was above water level, thus furnish- 

 ing a somewhat drained soil for the grow r th of more woody plants. 

 Consequently the amphibious species were forced to move on, and 

 their place w r as taken by woody trees and shrubs. This later 

 growth in turn built up a layer of autocthonous peat which shows 

 the remains of comminuted material, but none of the structures 

 so characteristic of the allocthonous layers below. In securing 

 these samples some difficulty was experienced in forcing the probing 



