CHAPTER XXX 

 DICKSONIACEAE 

 ///. Dennstacdtiinac 



Under the name Dennstaedtieae, Kuhn grouped together the genera 

 Hypolepis, Microlepia, Leptolepia, and Dennstaedtia, basing the relationship 

 chiefly upon the simple hairs which form their dermal covering (Kuhn, Die 

 Gritppe der Chaetoptevides, Berlin, 1882). With the addition of Saccoloina, 

 and on a broader basis of comparison, Prantl adopted this grouping under 

 the name Dennstaedtiinae {Ahhandl. d. Konigl. Bot. Gai't. Breslau, I, i). 

 But the old genus Dennstaedtia of Bernhardi had previously been merged 

 by Sir W. Hooker into Dicksonia, as '^Patania Presl, a fact which suffici- 

 ently indicates the similarity it bears to that genus, and particularly to the 

 species with a creeping habit: for the Dennstaedtiinae are themselves chiefly 

 prostrate. However, the detailed study of the Dennstaedtiinae as now con- 

 stituted, while it fully bears out the close affinity with Dicksonia, shows 

 features of advance which justify the maintenance of Prantl's distinct 

 grouping, while they also point in the direction of the two series characterised 

 by Davallia and by Pteris. Though Dennstaedtia was thus included by 

 Hooker under Dicksonia, Microlepia had been placed as a section of Davallia 

 {Syn. Filic. p. 97). The numerous synonyms which they have borne from 

 time to time in the writings of other systematists show how closely the two 

 genera are allied, and justify Prantl's grouping of them together. They 

 occupy a peculiarly interesting position as connecting links between the 

 basipetal sorus seen in Dicksofiia, and the mixed sorus of Davallia. In other 

 respects Saccoloma is also a leading outlier pointing especially toward 

 Pteris. For these reasons the Dennstaedtiinae will demand careful attention 

 as an important transitional series. 



These Ferns have for the most part a creeping habit, with solitary, long- 

 stalked, repeatedly pinnate leaves. The dermal appendages are hairs, 

 excepting in Saccoloma, which has broad scales. The sori are marginal, as 

 a rule distinct from one another, and slightly turned downwards, with the 

 upper protective flap larger than the lower. It has long been known that 

 the axes of Dennstaedtia and of Microlepia show the relatively primitive 

 solenostelic state. The vascular relations of leaf and axis in different species 

 of Dennstaedtia are indicated by Fig. 536, A, B, C. In all of them the 

 leaf-trace is an undivided ribbon-like strand. The stelar tube opens at its 

 insertion forming the leaf-gap, which is here short and soon closes {A). This 

 simple structure holds for most species, though the vascular supply for 



