330 POLYrODIACE^E. 



sori and in the upper portions half-groAvn ones, while in the uppermost por- 

 tions of the same frond there appeared the very beginning of sorus-formation. 

 In the beginning, the sorus (Fig. 137-g) looks like a mere depression of the 

 surface ; this depression grows larger and deeper and becomes cup-shaped ; 

 sporangia then first appear at the center of the cup. The depression grows 

 still deeper and larger, but the opening becomes narrower and narrower, and 

 at length the depression sinks down into the tissue forming a pouch-like cavity 

 with a linear orifice beset with bristles. In my specimens the orifice, quite 

 contrary to Fee's statement, is present at the very beginning of the sorus-for- 

 mation, but is not at all a slit which appears as a secondary result of the 

 bursting of the epidermis. The sorus-formation in the earlier stages is almost 

 the same as that of a normal Polypodium, but differs in having receptacles 

 in the depression. Such a depression is, by no means, absolutely exceptional 

 in Polypodium, as we see in P. repandulum, P. papillosum and others. P. 

 obliquatnm is simply an example of an extreme case having depressed sori. 

 Several stages connecting this extreme form and the normal one are repre- 

 sented by several species of the genus just as they are represented in one 

 series in the process of sorus-formation in one and the same frond. That 

 Cryptosorus is directly derived from a normal Polypodium is thus clearly in- 

 dicated. Consequently, there can be no doubt but that Cryptosorus is phylo- 

 genetically congeneric with Polypodium. The former is generally regarded as 

 a subgenus of the latter by leading pteridologists, such as BAKER, CHRIST and 

 others. 



Now turning again to Prosaptia, I shall consider the development of the 

 sori of P. Emersoni and P. celebica. These ferns also exhibit an indefinite 

 growth, representing several stages of sori in one and the same frond. Full 

 grown sori are located at the apex of the margin of the lobes with long U- 

 forni cavities with dorsally compressed orifices at the apex directed parallel to 

 the surface of the frond, and in every respect exactly like those of Davallia. 

 But, in the very beginning, the sorus-formation (Fig. 137, h-i) commences 

 with a depression at a little below the extreme edge of the margin on the 

 under surface, as may be seen nearly, if not exactly, in the case of Polypodium 

 obliquatum. As the sorus develops, the depression grows deeper and deeper 



