GLEICHENIACEAE 



557 



is some variety of detail, according to the size of the future sporangium ; 

 in the larger type of 67. cirri nata or Gl. Jlabellata 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 />, c). These divi- 

 sions do not appear to be uniform, as will be seen on comparison of the 

 four corners of Fig. 311 <-, and of vertical sections (Fig. 311 />}; the 



FIG. 311. 



a, 6, c = sori of Gleiclienia tlabcllata, n, b in vertical, c in horizontal section ; </, c,_f 

 sporangia of Gl. circinata showing i-tntral cell and tapetum ; , h, /=sori of Gl. _ 

 liic/wtotna ; in g the centre is vacant, in /; and / young sporangia appear in the vacant 

 space ; /, /<r = sporangia of Gl. JJabcllata with spore-mother-cells formed, and very 

 numerous, a - ix 200 ; j, X 100. 



latter also show in the case of these more massive sporangia that the peri- 

 clinal 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 67. diciiotoina the sporangium is from 

 the first of more elongated form, and its stalk less massive (Fig. 311 ,{,') ; 

 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 



