CHAPTER XXXIV 



DIPTERIDACEAE 



The genus Diptcris Reinw., so long merged in the comprehensive genus 

 Polypodiiun on account of its sorus being naked and superficial, has lately 

 been restored to an independent position, and is now held as the sole living 

 representative of the family of the Dipteridaceae (Seward and Dale, Phil. 

 Trans. Vol. 194, p. 487, 1901). There is no doubt that this position is 

 justified, though so late as 1902 the genus was still assigned a place among 

 the Aspidieae (Diels, E. and P. i, 4, p. 202): Christensen {Index, p. xxvi) 

 accepts the family as distinct, but ranks it under the xA.spidieae. It will be 

 shown that it takes its natural place among relatively primitive types in near 

 alliance to the Matoniaceae. 



The genus is represented by five living species from the Indo- Malayan 

 Flora. They have creeping rhizomes which show occasional dichotomy. 

 From these arise long-stalked alternate leaves, bearing each a distal lamina 

 repeatedly branched in a dichotomous manner, and with a marked median 

 sinus. The leaves of the different species vary greatly in area, but are alike 

 in plan. The segments may remain narrow, with a marked midrib, and 

 lateral flanges of no great width, as in D. Lobbiana Hook., and D. quinqiie- 

 furcata Baker (Fig. 572): or they may be broader, and be more or less 

 webbed into a continuous lamina, which is however still divided by the 

 median sinus into approximately symmetrical halves. This is seen in D. 

 conjngata Reinw. (Fig. 568, A), and D. Wallichii Hook, and Grev. Such 

 leaf-structure is comparable as a whole with that of Matonia. But while in 

 both the architecture is based upon helicoid sympodial branching, that in 

 Matonia is of the catadromic type while that of Dipteris is anadromic (see 

 Vol. I, Chap. V, Fig. 82, A, E). The same holds also, with peculiar modifi- 

 cations that give a very characteristic appearance, for the leaves of Dictyo- 

 phylluni and Caviptopteris. These are Mesozoic fossils referred by Nathorst 

 to a relationship with Dipteris (see Vol. I, Fig. 82, C, D. Also Nathorst, K. 

 Svensk. Vetenskaps-Akad. Hand, xli, No. 5). 



While the primary venation of the leaves of Dipteris is dichotomous, the 

 reticulation of the smaller veins is of an advanced type, viz. that described 

 as venatio anaxeti. The reticulation is initiated even in the juvenile leaves. 

 In Z>. Lobbiana though the first branchlets may end as "open" veinlets, in 

 the later leaves they are linked together into a reticulum (Fig. 569), while 

 in D. conjngata the very first leaves already show the complicated characters 

 of the adult (Fig. 570). Comparing these facts with what is seen in JSIatonia 



