XLV] PLEOPELTIS 225 



species PL angustata, the name being based upon the peltate scales that 

 protect its sori. The venation of the genus is anastomosing, having irregular 

 areolae, mostly with included veinlets spreading in various directions: the 

 sori are round or oblong. These features are broadly comparable with what 

 is seen in Neocheiropteris, and with the Dipteroids generally. They are 

 mostly wide-creeping, leathery-leaved Ferns, of epiphytic habit, and some 

 species are myrmekophilous, as in P. lecanopteris Matt., though this is often 

 maintained as a substantive genus (E. and P. I, 4, p. 326)^ The species more 

 particularly treated b>' Von Goebel were Pl.phyniatodes L. and PL nigrescens 

 BL, and the chief comparative interest centres round the sori. Suffice it to 

 say in general that in the long, tongue-like leaf-form, advanced stelar 

 disintegration, the prevalent sclereid-nests, and the general venation, Pleo- 

 peltis compares with the Dipteroid Ferns. The sori are of relatively large 

 area, and circular or oval in outline. The numerous sporangia, of mixed ages. 



2 ^ 3 



Fig. 732. /"/^^/g/Zw, after Von Goebel. 1=/'. m;^r£j-fe«j-, the plate of tracheides underlying 

 the sorus is shaded, the outline of the sorus dotted. i = P. phytnatodes, a " dictyosorus " in 

 surface view, its limit indicated by a dotted line. 3 = /". schradcri, the tracheidal plexus 

 beneath the dictyosorus is dotted. 



are interspersed with hairs, as they are also in the sori of Christopteris. But 

 here the hairs may assume the form of flattened scales, a development which 

 culminates in the peltate type seen in PL angiistata, or in PL macrosphaera 

 (Von Goebel, Lc Fig. 44). Glandular cells may appear at the apex or margin of 

 these, comparable to those seen on the clathrate scales of other related 

 Ferns (Fig. 728). 



Interesting features for comparison are found in the vascular supply 

 which underlies the sori. In Pleopeltis nigrescens the receptacle is wide and 

 flat, and a broad vascular plate underlies it, resulting from an enlarged 

 junction of converging primary veins of the blade. This state might readily 

 follow from widening of a punctiform type of sorus (Fig. 732, i). The structure 

 seen in PL pliymatodes is more complex. The sorus is again circular or 

 oval, and of large area. Branches of the primary venation here also form a 

 junction below the receptacle, but the intra-areolar veinlets also take part, 

 enlarging their ends, which terminate blindly, with or without branching. 

 The receptacular area thus covers a considerable plexus of veins, sporangia 

 being borne on the leaf-surface between the veins, and extending even 



1 A full description of its habit and structure has been given by Yapp {Ann. of Bot. XVI, p. 185. 

 See also Vol. i, Fig. 50). 



