XXXVI] HYPOLEPIS 1 



draws a clear distinction between Hypolepis on the one hand and Cheilanthes, 

 according to the form of the spores, which he describes as spherical-tetrahedral 

 ("kugelformig-tetraedrisch") in the former, and spherical-quadratic in the 

 latter ("kugel-quadrantisch"). He does not hesitate to bring forward this 

 distinction, since it appears in all the species of the two genera, while other 

 characters are very fluctuating. Moreover he extends it to Plecosorus, which 

 he ranks with Phegopteris and the Aspidieae. If those who followed had given 

 more attention to habit-characters and development, Hypolepis might have 

 arrived sooner at some more fixed systematic position. Evidently Diels was 

 dissatisfied with its place among the Cheilanthinae, for he remarks [I.e., p. 277) 

 that Hypolepis has in habit little in common with the other t3^pes of this 

 series. To us who now realise that a very similar soral structure may arise 

 along distinct phyletic lines, the habit-characters acquire additional value in 

 these comparisons. It seems probable that the sorus of Hypolepis may have 

 come from some bi-indusiate Dicksonioid source by abortion of the inner 

 indusium, while that of Cheilanthes may have been uni-indusiate from the 

 first (Fig. 582, B, D). Already Kuhn (1882) and Prantl (1892) had placed 

 Hypolepis in the newly erected group of the Dennstaedtiinae. An examination 

 of the genus, from the developmental point of view, shows that this is 

 probably the natural place, though as its most detached member. 



The habit-similarity oi Dennstaedtia and Hypolepis appears in the creeping 

 rhizome with relatively long internodes and ample upright-growing leaves, 

 of high pinnation and finely cut: the vestiture consists of hairs only: and 

 each of the numerous sori is seated in a sinus of the margin. Both rhizomes 

 are solenostelic. Gwynne-Vaughan has demonstrated the similarity of the 

 vascular system of species of Dennstaedtia (Vol. II, Fig 536) to those of 

 Hypolepis (Fig. 583). The latter, however, being smaller show no advance 

 towards polycycly such as appears in the larger Dennstaedtias (Vol. II, 

 Fig. 537), and notably in the erect Saccoloma (Vol. II, Fig. 538). But there 

 are other indications of advance, for instance occasional interruptions of the 

 continuity of the otherwise undivided leaf-trace are seen. These are of the 

 nature of perforations, which appear also in the solenostele of some Denn- 

 staedtias. They may be held as signs pointing towards that disintegration 

 which is a marked feature in the vascular system of Davallia. Incidentally 

 it may be noted that the supply to the lateral branches in Hypolepis is 

 marginal in origin, not abaxial as in the Cyatheoid Ferns (Fig. 583). 



The chief distinction between Dennstaedtia and Hypolepis lies in the sorus. 

 That of Dennstaedtia is cup-like, and indistinctly two-lipped, while that of 

 Hypolepis, though corresponding to it in position, has only a single lip, viz., 

 the upper or adaxial, which curves more or less over the receptacle, and is 

 rather membranous in texture (Fig. 582, B, D). It has been described as 

 "formed out of the reflexed margin" {Syn. Fil. p. 128). The converse of this 



