224 DIPTEROID FERNS [CH. 



by the overlapping peltate scales (38). Mucilage-glands are found on the 

 margins of the scales (40, 41): these may be compared with those shown in 

 various Ferns of Dipteroid affinity (Fig. 728). 



The vascular system contracts below the fertile region of the sporophyll: 

 but branches, non-existent in the sterile blade, enter the receptacle in a plane 

 below that of the primary system, and pursue a course below the coenosori 

 (36, 37, 3s)- To those who have followed the origin of the diplodesmic state in 

 Cheiropleiiria, Platycerium and Christopteris it will be apparent that this is 

 a diplodesmic state, cognate with their subsoral developments, but it is 

 carried out in a leaf that is more contracted. The sporangia are of an 

 advanced Leptosporangiate type, with a three-rowed stalk. 



Professor Von Goebel discusses the relation of Hyuienolepis spicata to 

 Pleopeltis rather than to the Dipteroids. By arguments that appear con- 

 vincing he assigns to it a near relation to that Section of Polypodioid Ferns. 

 But a broader interest lies in the fact that it may now be accepted as a 

 synthetic type, linking the Dipteroid and Matonioid Ferns with a Section 

 of the comprehensive genus "■ Polypodimnr The Dipteroid affinity of 

 Hymenolepis is no new suggestion: the genus was placed by Christ next to 

 Cheiropleuria in his Farnkrduter (p. 129). But Diels included it in the 

 Taenitidinae {I.e. p. 305), a group which Von Goebel regards as unnatural 

 and therefore he detached it {I.e. p. 148). To this a ready assent may be 

 given. Alternatively, the new facts support a near relation of Hymenolepis 

 to Christopteris, the differences between them being such as their difference 

 of habitat might be expected to induce: for the former is epiphytic while 

 the latter is a ground-growing Fern. 



Pleopeltis 



In my Studies VI {Ann. of Bot, 1917, p. 18), writing on the Dipteroid 

 derivatives, the probability was pointed out that many Polypodioid Ferns 

 would find their phyletic grouping with them. This opinion was based on 

 form, venation, anatomy, and soral characters: in particular comparison was 

 then made between Neocheiropteris and Polypodinni {PJilebodiimi) deeiimaniim 

 Willd. as regards the lobation of the broad blade, so clearly Dipteroid in its 

 character. Such comparisons form a natural introduction for the new facts 

 relating to Pleopeltis disclosed by Von Goebel in ig26{Ann.Jard. Bot. Btiit. 

 Vol. XXXVI, p. 107). But Pleopeltis gives a closer comparison with the 

 Dipteroids than does Phlebodinni, both on the ground of venation and of 

 geographical area : for it is richly represented in the Malayan region, while 

 PJilcbodiuni is absent. 



The Section Pleopeltis of '^Polypodinni',' as described by Van Rosenburgh 

 {Malayan Ferns, 1909, pp. 623-675), includes over 100 species in the Malayan 

 region. The genus was founded by Humboldt and Bonplond for the American 



