26 DAVALLIOID FERNS [CH. 



The sori of Tapeinidium are as a rule separate, and slightly intra-marginal, 

 and each is seated on the end of a vein. The upper indusial lip appears as 

 a projecting tooth of the leaf-margin, the lower as an intra-marginal cup (Fig. 

 595, H,J). The development of the sorus has not been followed, but probably, 

 as in Odontosoria and Lindsaya, the origin of the receptacle will prove to be 

 marginal, with signs of a gradate sequence of the sporangia. The confluence 

 of the sori laterally appears to be a variable feature: the interest lies in the 

 fact that it exists. Fig. 595, H shows two sori with a confluent upper in- 

 dusium: the fusion may, however, be carried out in various ways. Separate 

 sori are the rule, though fusion would be a natural sequel to leaf-condensa- 

 tion. Such details of habit, anatomy, and sorus explain the wide synonymy 

 of these Ferns, since they resemble a number of other types. Of the Daval- 

 lioid affinity there can be no doubt, but the actual phyletic relation is best 

 left open by maintaining Tapeinidium as a substantive genus. 



DiELLlA Brackenridge 



This genus is endemic in the Hawaiian Islands, and comprises some seven 

 species. It has been associated by most writers with the Davallioid Ferns: 

 Hooker included it as a section of the genus Lindsaya {Syn. Fit. p. 1 1 2). But 

 it is maintained as a substantive genus by Diels and by Christ, the diagnostic 

 points being that in Lindsaya the leaf-segments are unilateral, while in 

 Diellia they are obliquely triangular: also that the indusium of Diellia is 

 broadly adherent: this distinguishes it from Leptolepia, where the adhesion 

 is limited to the vein. The three genera, together perhaps with Saccoloma, 

 form a close nexus, the least specialised species having many points in 

 common. 



Diellia has either an upright or a creeping rhizome, covered by broad 

 scales, which extend to the petiole. The leaves present various forms sug- 

 gestive of condensation from a more highly pinnate state. The lateral veins 

 usually fuse, sometimes only here and there (D. falcata Hk.), sometimes 

 they are highly reticulate {D.puinila Brack.). The sori are more or less deeply 

 intra-marginal, with a membranous lower indusium. They are usually borne 

 separately on the widened vein-endings: but in many species occasional 

 linkages occur, and in D. falcata and D. erecta these are frequent, especially 

 at the bases of the pinnae. 



The genus has not hitherto been examined anatomically : it was therefore 

 a special pleasure to receive from Dr H. L. Lyon a supply of D. falcata 

 from Hawaii. In this species the rhizome is obliquely ascending, with 

 leaves spirally disposed. The rhizome and young leaves are covered by 

 dark brown, closely imbricated scales, while others of more delicate form 

 extend up the petiole. The stem contains a rather rudimentary dictyostele 

 with sometimes two, sometimes three, leaf-gaps in the single section: in 



