Yapp . — Two Malayan ‘ Myrmecophilous ’ Ferns. 2 1 9 
Treub 1 for the galleries of Myrmecodia . He supposed that 
aeration of the fleshy tissues of the swollen stem is affected by 
means of these moist chambers, without an undue loss of 
water. Haberlandt 2 adopts this view, but Goebel 3 remarks 
that while there is much to be said for it, yet the need for this 
elaborate mechanism for the interchange of gases is, in the 
case of Myrmecodia , by no means proved, especially as the 
tuber is not green, and therefore cannot assimilate. Karsten 4 
is of the opinion that the galleries of P . sinuosum serve for 
the purpose of aeration. 
Now in spite of the fact that the younger parts of the 
rhizomes of these Ferns contain chlorophyll 5 , there appear 
to be no stomata on the stem. Moreover, the system of 
intercellular spaces usual in massive tissues 6 is here almost 
entirely absent 7 . To whatever cause this latter fact is to be 
ascribed 8 , it would seem possible that in a tissue which is 
practically devoid of the usual adaptations for gaseous inter- 
1 Treub (’88), p. 206. 2 Haberlandt (’96), p. 350. 
3 Goebel (’89), p. 212. 4 Karsten, loc. cit. 0 
5 This is certainly true for P. carnosum, and I believe for P. sinuosum also. 
e Devaux (’91), p. 31 1. 
7 The rhizomes of several other Ferns (i. e. Polypodium conjugatum, P. aureum , 
P. quercifolium and Davallia Fijiensis ) were examined. The intercellular spaces 
varied considerably in size in different species, in some being very minute, but in 
each case they were better developed than in the two species under consideration. 
8 External conditions, resulting in the marked xerophytism of these Ferns, may 
perhaps be sufficient to account for this [cf. Stahl (’83), p. 17, on the relative sizes 
of intercellular spaces in sun and shade leaves]. It is also conceivable that the 
absence of intercellular spaces may be a more or less mechanical effect, due to the 
formation of the aqueous tissue itself. This tissue, when alive, usually contains 
large quantities of water. Now even a thin-walled cell, when perfectly turgid, 
can exert an enormous outward pressure [cf. Pfeffer (’00), p. 139]. Such hydro- 
static pressure (aided perhaps by the growth and division of the cells immediately 
surrounding the aqueous tissue) exerted at a time when the remaining tissues of the 
stem were soft and plastic, might possibly inhibit to some extent the formation of 
intercellular spaces. The crushed appearance of many of the ground-tissue cells, 
seen more especially in the partitions between adjacent galleries, as also the fact 
that in P. sinuosum the walls of the small cells surrounding the galleries have 
their stoutest thickening bands more or less radial in position [cf. Baranetzki (’86), 
p. 199, on the mechanical principle involved], would seem to point to some such 
force having acted radially outwards from the region occupied by the aqueous 
tissue. 
t Q 2 
