19S BOTANICAL GAZETTE [march 



a light brown spongy nature. Fig. 6 presents a preparation from 

 this material, and it will be seen that there are many parts of plants 

 in a perfect state of preservation due to a perpetual covering by 

 water. Other structures more definitely related to lake peats are 

 idioblasts and parts of insects. 



Florida is especially favorable for studies of this type of peat, 

 owing to an abundance of "saw grass" {Cladium) marshes about 

 Lakes Harris, Griffin, Apopka, and in fact generally throughout the 

 Everglades. If one were to rely solely upon a superficial examina- 

 tion of this material, representative of the later stage in herbaceous 

 marsh development, he would reach the conclusion that these 

 deposits have been formed by a growth of herbaceous plants in 

 situ. A detailed examination of samples from different depths, 

 however, shows that this is not a correct interpretation. On the 

 contrary, these paludal accumulations, with the exception of the 

 uppermost layers, are obviously allocthonous. A sample secured 

 3 ft. from the bottom of the marsh bordering Lake Harris is pictured 

 in fig. 7. This illustrates conclusively that the material has not 

 been formed in situ by a gradual amassing of fallen plants, but 

 rather by a floating together of drifted and wind-blown matter 

 similar to that characteristic of deeper lake deposits, as indicated 

 in figs. 1-4. The usual structures found in lacustrine peat, shown 

 in fig. 7, are pollen grains, idioblasts, plant fragments, ejecta, and 

 formless drift. Although no sponge spicules and diatoms appear in 

 the illustration, it should be added that they are of common occur- 

 rence. This kind of peat is usually encountered in the lower four- 

 fifths of "saw grass" marshes, as determined by vertical series of 

 samples. The upper layer, nevertheless, has been accumulated in 

 a different manner, since the microscope reveals only the tangled 

 remains of fallen herbaceous plants, and the structures usually 

 found in open water deposits are conspicuously absent. It is prob- 

 able that this distinct change in the process of deposition was 

 accomplished at some time when the material had so collected that 

 the mass w r as above w r ater, for a part of the year at least, so that 

 plants perishing in place were allowed to become more or less 

 reduced owing to exposure, and not permitted Jo float away and 

 become precipitated among the usual sedimentary detritus. It is 



