I04 DRYOPTEROID FERNS [ch. 



Hypoderris R. Brown 



This West Indian genus now includes three species. That first to be dis- 

 covered was H. Brownii J. Sm., which was related by Brown to Woodsia on 

 account of its indusial character. Notwithstanding the difference of habit, 

 and as we shall see certain features of soral detail, there has never been 

 reason to reconsider this relationship. Hypoderris may be held as a low- 

 country representative of the family, with leaves adapted to a shady habit, 

 and with sorus advanced to a mixed condition. 



The creeping rhizome bears solitary leaves right and left, the surface of the 

 shoot being invested by soft brown scales. The leaf is broadly lanceolate, 

 often with two lateral lobes at its base, of variable proportion. But occasionally 

 the blade may be five-lobed, resembling that of Christensenia (B.M. specimen 

 from Trinidad H. Prestoc): on the other hand it is usually simply lanceolate. 

 The margin is frequently sinuous. The richly reticulate venation is of the 

 Drynarioid type, and the numerous sori with basal indusium are inserted 

 in lines or series parallel with the primary veins (Fig. 646, F). The thick 

 sappy axis is traversed by a dictyostele with large leaf-gaps, and there are 

 also wide-meshed perforations, the latter chiefly on the upper and lower 

 faces. The leaf-traces consist of four strands, each pair right and left repre- 

 senting one of the two strands of Woodsia. These facts, together with the 

 reticulate venation, indicate a state of advance on that seen in Woodsia. 



The soral condition of Hypoderris confirms this. The position of the sorus 

 is variable: commonly it is seated upon an arch of the main reticulum, but 

 sometimes on a smaller twig, or even on a vein-ending (Fig. 246, G, H). 

 At first the flat receptacle is almost continuous with the general leaf- 

 surface, being fenced off by the fimbriated cup-like indusium before the 

 sporangia appear. These arise sporadically over its broad surface, without' 

 any obvious order. Fresh sporangia following on those first formed continue 

 thus to arise till the sorus is crowded, while the heads of those earlier 

 matured break away, leaving their stalks to 

 protect those that follow. Thus a section of an 

 old sorus appears similar to that of certain 

 Mixtae of quite different affinity, excepting for 

 the basal indusium which is clearly like that of 

 the Woodsieae. Such facts suggest that sorally 

 Hypoderris is a Cyatheoid derivative that has 

 assumed a mixed sorus. The very numerous F'g-.M- Young sporangia of //j//<p- 



•' dents Brownn, showing three types of 



sporangia are small and long-stalked. The segmentaiionaccordingtosize(^,^,C): 



. 11 ^ 11 J • 1- below are the corresponding stalks, A 



Stalks may appear i, 2 or 3-celled m transvei.se .insisting of one, C of three rows of 



section (Fig. 649). This condition arises from cells, (x 175.) 



the initial segmentation, which is not uniform. Young sporangia of three 



