Yapp . — Two Malayan ‘ Myrmecophilous ’ Ferns . 2 1 1 
the branches, but in P. sinuosum the latter being much less 
numerous than in P. carnosum , the lateral galleries are not 
developed with such regularity. Sections, however, taken 
through those lateral projections of the stem which we have 
seen are to be regarded as undeveloped branches, show 
pocket-like diverticula of the main gallery extending into 
them (d in Figs. 24 and 27). 
Each leaf-cushion contains a single vertical gallery (oblong 
in cross-section) which ends blindly some distance below the 
leaf-articulation. Just after leaving the main gallery, it 
sends out a single diverticulum which does not branch, but 
travels backwards in a straight line for a distance of about 
1 cm., and ends blindly in a blunt point. There is usually 
an external swelling on the stem corresponding to this 
diverticulum (Figs. 29 and 36). 
The relation of this dorsal chamber to the vascular system 
differs from the arrangement found in P. carnosum . In both 
Ferns the vertical gallery passes outside the vascular cylinder 
through a foliar gap, but while in P. carnosum the diverticulum 
given off from this gallery is directed forwards, and passes out 
through the gap left in the network of foliar bundles, that of 
P. sinuosum is directed backwards, and does not pass to the 
exterior of the vascular system at all, as the foliar bundles 
form a vaulted network over it. 
The gallery system communicates with the exterior both by 
the dying-off of the older parts of the stem 1 ) and also, as in 
P. carnosum , by means of small lateral or ventral openings 
made by the ants themselves. 
b. Root. The root of P. sinuosum is an almost exact 
counterpart of that of P. carnosum , but on a smaller scale. 
The outer cortex is only about three or four cells thick, 
including the piliferous layer. The walls of its cells possess 
the same prominent network of thickening bars as do those of 
P. carnosum , while the cells of the inner cortex form a scleren- 
chymatous stelar-sheath of precisely the same nature. 
c. Leaf. The petiole is generally almost circular in transverse 
1 Goebel, loc. cit., p. 17. 
