XX l] 



HABIT 



129 



Fig. 418. Abnormal sporelings of Osmunda regalis 

 showing indeterminate structures between leaf and 

 shoot. In A, a leaf-blade and a bud {b) are borne on 

 a common stalk; in R, there is no leaf-blade, and the 

 bud (b) is as before raised upon an indeterminate stalk. 

 (.-/X3; -5X4.) (After Lang.) 



specialised. But in Osmunda the sporangia are localised on various fertile 

 parts of the leaf which then show a smaller expanse of surface, while the 

 sporangia are seated at or near to the margin. This fertile region may be 

 distal as in O. regalis, or intermediate as in O.javanica and others (Fig. 419). 

 The sporangia, which are numerous and large, are of pear-like form, and 

 those in near proximity to one another originate simultaneously: there is 

 no interpolation or marked sequence in origin. In Osmunda they are borne 

 in approximately marginal tassels without any regularity of orientation. 

 Sometimes intermediate states between sterile and fertile pinnules occur, 

 with larger leaf-surface, and with the sporangia attached superficially 

 (Fig. 420). This leads to the state seen in Todea, where the sporangia are 

 borne only on the under surface: their arrangement has some relation to the 

 veins, but again there is no common rule of orientation. These Ferns are 

 then non-soral. The conditions seen would be consistent with the sporoph)'ll 

 having been originally narrow, and the sporangia borne at or near to the 

 margins; but that with increasing leaf-area they passed to a superficial posi- 

 tion. Comparison with the Coenopterids would support this hypothetical 

 interpretation. The sporangia, which are large and thick-stalked, consist at 

 maturity of a single layer of cells forming the wall, but with a few tabular 

 cells remaining within. A group of polygonal thick-walled cells in a: lateral 

 position near the distal end is recognised as an annulus. It is related to the 

 slit of dehiscence so that the latter passes from the centre of the annulus 



B. II. 9 



