234 BOTANICAL GAZETTE [APRIL 
shrunken and contorted, their nuclei broken down, and the cyto- 
plasm disorganized. 
A study of the ligule of Isoetes to be complete must be 
accompanied by a comparative examination of the ligule of 
Selaginella. With this in view I have studied the origin and 
growth of the ligule in S. Martensii and S. apus, and compared 
my sections with the excellent drawings of Professor Harvey 
Gibson (2). Professor Farmer (1) has expressed the view that 
the ligules of Isoetes and Selaginella have little in common 
except their position and name. I have been led to quite the 
contrary conclusion, to hold in fact that there is a very close 
homology between the two. What has appealed most to me, 
in addition to the position of the organs, is the similarity of the 
regions of which both are seen to consist. The ligule of Selag- 
inella has a glossopodium of large empty cells, sheathed by a 
gland-like layer, and shows also two upper regions, one of living . 
and one of disorganizing cells. The two are alike also in the 
absence of chlorophyll, starch, and intercellular spaces; and 
both show their embryonic character by passing their maximum 
of growth before the leaf has reached its greatest functional 
activity. Differences are to be expected, of course, and are 
chiefly these: the ligule of Isoetes arises from a single cell, that 
of Selaginella from a group of cells; and, whereas the ligule 
of Isoetes is almost from the beginning a conspicuous part of the 
leaf, that of Selaginella is rather late in making its appearance, 
no trace of it being discoverable until after the sporangium rudi- 
ment is plainly perceptible. 
THE SPORANGIUM. 
The sporangium has repeatedly been made the object of 
investigation during the last fifty years. Hofmeister (1) was 
the first to make a careful study of its origin and development. 
Though his view that the sporangium can be traced back to 4 
single cell has been discredited by later observers, I hope to show 
that his error was largely due to his exclusive dependence upon 
longitudinal sections. Except for his failure to see the true 
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