XII 



THE SIMPLE SORUS 



209 



6 c e / 



c a 



Fig. 199. Zygopteris [Etapteris). i, group of four sporangia on a common 

 pedicel {a), x 10. 2, two sporangia on pedicel. The upper shows the annulus 

 {c) in surface view, with spores exposed aty": the lower in section, x 10. 2 bis, 

 sporangium cut in plane of annulus. 3, group of sporangia in transverse 

 section, x 20. Lettering common to the figures. « = common peduncle: 

 ^ = sporangial wall: f = annulus: ^ = tapetum (?):/= spores : w = pedicel of 

 individual sporangium : n — probable place of dehiscence. (All after Renault.) 

 (From Scott's Studies in Fossil Botany^ 



of the vein, room may be found for an increased 

 number of sporangia. This is illustrated in the 

 Marattiaceae, where in Angiopteris and Marattia 

 the sorus is oval with relatively few sporangia 

 (Fig. 202); but in Archangiopteris and in Danaea 

 it is more elongated, and the number of sporangia 

 is great (Fig. 202). Thus, while preserving the 

 same type of simple and uniseriate sorus, the 

 number of sporangia may be either reduced or 

 increased. 



Fig. 200. GleicheniajiabeUata,^x. Midrib and three 

 pinnules, showing the arrangement and constitution 

 of the sori, with a variable number of sporangia. 



