54 STUDIES IN FOSSIL BOTANY 



placed, surrounds the stalk of each peltate scale (see 

 Fig. 21). 



The sporangia are elongated sacs, stretching back 

 from the lamina to the axis (Figs. 18 and 20). The 

 sporangial wall, as preserved, is usually only one cell 

 thick, and the lateral membranes of its cells are stiffened 

 by projecting ridges (Fig. 22). When cut across, these 



Fig. -zo.—Calamostachys Binneyana. A single peltate sporangiophore, in longitudinal 

 section, sin, sporangia, attached at a to the edges of the peltate lamina. They 

 are full of spore-tetrads. X about 40. S. Coll. 174. (G. T. G.) 



buttresses are not easily distinguished from the cell- 

 walls. 



In Calamostachys Binneyana the spores are very 

 numerous in each sporangium, and, so far as has been 

 ascertained, were all of one kind, the average diameter 

 of the full-grown spores being about .09 mm. Curiously 

 enough, we often find them united in groups of four, the 

 tetrad being still enclosed within the membrane of its 

 mother-cell (see Fig. 22, A, B, C). Hence we see that 



