CHAPTER XXXVII 



DAVALLIOID FERNS 



The Davallieae stand as Tribe IV in the systematic scheme of Christensen's 

 Index, which restates in convenient form the arrangement of Diels {Natiirl. 

 Pflanzenfain. 1, 4, p. 204). The Family is there held to include fifteen genera : 

 but of those Dennstaedtia, Microlepia, Leptolepia, and Saccoloma were grouped 

 with Hypolepis as the Dennstaedtiinae by Prantl, and this separation has 

 been upheld here for reasons explained in Chapter XXXI, Vol. II. These genera 

 have there been ranked as a Tribe of the Dicksoniaceae, but with Saccoloma 

 and Hypolepis detached from the rest by somewhat more advanced features. 

 The remaining genera of the Davallieae group themselves naturally round 

 Davallia, which may be held as a central type of those more advanced 

 Dicksonioid derivatives where the individuality of the sorus is as a rule 

 maintained. 



Davallia Smith 



The genus Davallia (excl. Prosaptia) includes about 60 species, as stated 

 in Christensen's Index, which inhabit the warmer regions of the Old World. 

 They are mostly of creeping habit, and are often epiphytic. The leaves are 

 solitary, and usually highly pinnate, with open venation. The rhizome bears 

 protective scales. The sori are seated separately on the ends of the veins, and 

 are more or less intra-marginal, a condition which compares with what has 

 been seen in some of the Dennstaedtiinae. But a distinctive feature is that 

 the lower indusial margins are fused with the leaf-surface, giving a pocket- 

 like form to the sorus (Fig. 588, /, K). Anatomically the genus Davallia 

 itself is more advanced than any of the Ferns hitherto described. The 

 rhizomes are frequently massive and fleshy, having little or no sclerenchyma. 

 The vascular system is seen in transverse section of the rhizome to consist 

 of a circle of meristeles, of which two are larger than the rest and flattened : 

 these run parallel to the upper and lower faces of the rhizome. The circle is 

 completed by a number of smaller strands which have been cut through in 

 their course towards the alternately lateral leaf-bases. There are in fact two 

 lateral rows of alternating leaf-gaps, and from the margin of each gap separate 

 vascular strands arise, which represent a much-divided leaf-trace. Their 

 nature as such is shown by their passage outwards, with varying anastomoses 

 among themselves, into the bases of the petioles (Fig. 589). 



There is some variety in the stelar structure of the Ferns which have been 

 ascribed to Davallia: and the divergences from the highly segregated state 



