GLEICHENIACEAE 557 
is some variety of detail, according to the size of the future sporangium ; 
in the larger type of G2. avcinata or Gl. flabellata each process under- 
goes segmentation, resulting in a conical sporangial cell (x); in this 
successive obliquely inclined divisions follow, the earlier of which con- 
tribute to form the relatively massive stalk (Figs. 311 2, c). These divi- 
sions do not appear to be uniform, as will be seen on comparison of the 
four corners of Fig. 311 c, and of vertical sections (Fig. 311 4); the 
Fic, 311. 
a, 6, c=sori of Gleichenia flabellata, a, 6 in vertical, c in horizontal section ; @, e, f= 
sporangia of Gl. ctycinata showing central cell and tapetum; g, 2, 7=sori of GZ. 
dichotoma ; in g the centre is vacant, in # and 7 young sporangia appear in the vacant 
space; 7, #=sporangia of G/. flabellata with spore-mother-cells formed, and very 
numerous. @-72X 200; 7, #X 100. 
latter also show in the case of these more massive sporangia that the peri- 
chnal division, which cuts off the cap-cell, takes place at a time when 
the sporangial head projects but slightly from the surface of the receptacle. 
From this description, and from the figures it is apparent that the whole 
Sporangium is from the first of more massive construction, and results 
from more numerous segmentations than that of ordinary Leptosporangiate 
Ferns, though the last segmentations which define the central cell follow 
the usual sequence. 
In the more attenuated type of G/. dichotoma the sporangium is from 
the first of more elongated form, and its stalk less massive (Fig. 311 g) ; 
the formation of the cap-cell takes place at a time when the sporangial 
head is more clearly in advance of the adjoining tissue, and the central 
