208 Yapp . — Two Malayan ‘ Myrmecophilons' Ferns . 
about the level of each leaf-cushion, on the opposite 1 side 
of the stem, a slight lateral projection (a t Fig. 7). These 
projections sometimes develop into lateral branches, but more 
often lie dormant. As a result of this limited branching, the 
rhizomes never form a compact, solid mass such as is seen 
in P. carnosum , though they may overlap each other to 
a considerable extent 2 . 
(/ 3 ) Leaf. The fronds are sub-dimorphic, entire, glabrous 
and sub-coriaceous. The petiole and the midrib are brown. 
Sterile fronds 9-12 cm. long (including petiole), and about 
2 cm. wide ; elliptical-oblong to oblong, obtuse, margin 
entire, gradually narrowed at base into the petiole, sometimes 
cuneate. 
Fertile fronds 11-22 cm. long, 1-1*5 cm * broad; linear- 
oblong, obtuse, margin minute, base as in sterile fronds. Sori 
about 4-5 mm. long, oval or oblong, often becoming nearly 
circular towards apex of frond. They are rather deeply 
sunken (the pits producing oval projections on the upper side 
of the frond), and are arranged in a single longitudinal row on 
each side, nearer the margin than the midrib. 
The venation is of the same type as that of P. carnosum , 
but the costal areolae are longer and narrower in P. sinuosum 
(Figs. 47 and 48), and in the sterile fronds the larger areolae 
may contain smaller ones, formed by the anastomosis of the 
enclosed veinlets. 
Petiole 2-3*5 cm. long, approximately circular in cross- 
section. 
Internal Structure. 
The structure of P. sinuosum closely resembles in many 
respects that of P. carnosum , and need not be described in 
very great detail. Only those points in which the two Ferns 
differ markedly from each other will be dealt with at any 
length. 
1 In P. carnosum the branches arise at about the level of the leaf-cushions of 
the same side. 
2 Cf. Mr. Parish’s remarks in Hooker (’64), p. 62. 
