210 Yapp.— Two Malayan 1 Myrmecophilous ’ Ferns . 
The stele is of the same type as that of P. carnosum . The 
pericycle, in this case also a false one, as it originates from 
the same layer as the endodermis, is here only one layer 
thick throughout. The sclerenchymatous sheath is similar, 
but the radial pit-canals are often much more branched than 
is the case in P. carnosum. 
In the material at my disposal the impregnation of the 
cell-walls by phlobaphene is most marked in the two or 
three layers of small cells surrounding the galleries, the 
general ground-tissue never assuming the deep brown colour 
found in P. carnosum : this, however, may be due to the fact 
that my material did not include any very old pieces of stem. 
Moreover, the thickening of the cell-walls by bands is largely 
confined to these small cells. In P. carnosum, on the other 
hand, the small-celled zone seldom, if ever, has the thicken- 
ing bands developed on its cell-walls to any extent. Probably 
correlated with the early thickening of the walls of these 
small cells in P. sinuosum is the fact that although the 
cells do divide in early stages of growth, yet this division is 
never carried so far as in P. carnosum. Thus the curious 
projections of the small- celled zone between the large cells 
of the aqueous tissue (which originates in a similar manner 
in both Ferns) are never found in P. sinuosum. 
The aqueous tissue finally breaks down and forms galleries 
similar to those of P. carnosum. 
The arrangement of the ant-galleries in P. sinuosum has 
been described by Goebel 1 , but a few points may be added to 
his description, and a comparison made with the gallery-system 
of P. carnosum. As in P. carnosum , there is a single main 
ventral gallery, three or four times as wide as deep. It is seen 
in transverse section in Figs. 24 and 25, in median vertical 
longitudinal section in Fig. 28, and in horizontal longitudinal 
section in Fig. 27. Laterally it gives off side-galleries to 
condition of the vascular cylinder) of P. carnosum may be correlated with its very 
exposed situation, which renders it liable to intense insolation. It cannot, how- 
ever, be assumed, merely on general grounds of this sort, that originally the stems 
of the two Ferns were precisely similar in this respect. 
1 Goebel (’88), p. 16. 
