1 98 Yapp. — Two Malayan ‘ Myrmecophilous 9 Ferns . 
relatively small, brown cells. The development of these 
smaller cells is most marked at those angles which form the 
meeting-point of several of the outermost large cells. The 
result of this is that projections (occasionally of considerable 
length) of the small-celled tissue are found extending between 
the large cells. Thus the peripheral cells of the large-celled 
tissue come at length to occupy pocket-like depressions in 
the small-celled zone. This arrangement can perhaps be 
rendered more intelligible by the aid of figures. The inward 
projections of the small cells are seen in longitudinal section 
in Figs. 9 and 12. Fig. 10 represents a section taken parallel 
to the surface of the small-celled tissue, and passing trans- 
versely through the free ends of a number of these processes. 
A section in the same direction, but nearer the periphery 
of the large-celled tissue, is seen in Fig. 11 ; this shows 
several of the pocket-like depressions in the zone of small 
cells, occupied by some of the outermost large cells. 
During life the cells of the large- celled tissue are filled 
chiefly with water, their thin walls being merely lined by 
a film of protoplasm. The tissue thus probably functions as 
a water reservoir 1 . In appearance it strikingly resembles 
the special water-storing tissue of some desert plants 2 . 
Finally the large-celled tissue breaks down, and is rapidly 
disintegrated, its place being taken by the ant-galleries. In 
my material the aqueous tissue was rarely intact at a distance 
of 2 cm. from the apex of the stem, and was often entirely 
broken down before that point. Fig. 12 is a microphotograph 
of a section taken through some partially broken-down 
aqueous tissue. 
Arrangenient of the galleries. The system of galleries 
thus formed by the breaking down of the large-celled tissue, 
1 The translucency of the tissue, the thinness of its cell-walls, and the absence 
of intercellular spaces, all point to its being a true aqueous tissue. Cf. Warming 
(’ 96 ), p.199. 
2 Cf. Volkens (’ 87 ), p. 59. Figs. 2, 3 and 4 on Taf. XII show a very similar 
tissue in the stems of several flowering plants. The resemblance is increased in 
these cases by the similar ingrowths of a small-celled tissue between the large 
cells. 
