1888. | BOTANICAL GAZETTE. 175 
with a part of the peltate scale and of the stalk: a@, portion 
of the scale-stalk ; 4, section of the transverse cells of the 
ventral wall of the sporangium; c, section of the dorsal wall 
of the sporangium; below the sporangium is the scale in 
which the fibro-vascular bundle is seen to end. The spiral 
cells of the dorsal surface are continuous with the epidermal 
cells of the scale. Occasionally a spiral or annular celi is 
found in this epidermis. ig. 6 is a transverse section of a 
sporangium-wall, midway between base and apex. In three 
positions—one dorsal and the other two lateral—the wall is 
strengthened not only by an increase in size of the spiral 
cells, but also by a greater number of the inner or lining 
cells. As we approach the region of the ventral transverse 
cells, the sporangium-wall becomes thinner and thinner by the 
decrease in number and size of the lining cells. Sometimes— 
as shown in fig. 6 at a—the lining cells can be seen to be con- 
unued across the external transverse cells; but here the in- 
her cells are always reduced to a single very thin layer. 
Usually this layer of lining cells disappears in the ventral 
region; for it becomes closely appressed to the transverse 
) 
ternal cells of the wall, it is evident that the sporangium will 
Contract in length much more along the dorsal than along 
the ventral surface. In fig. 3 the position of the line of de- 
arrange- 
hould 
‘scence to move to the position indicated in fig. 
ted line 
ore from its original position. J 
happens, as es by fig. 2, which gives the ss sea 
an Open sporangium. 
2 
Annales des Science, 7 Series, Tome 2. 
