the Mycorrhiza of the Marattiaceae. 
81 
host-cells. But a curious effect is produced upon many of the large paren- 
chymatous cells of the inner cortex, which are stimulated to further division, 
as is shown in Text-fig. 3, a, b. 
However, on reaching the inner layers of the cortex, the hyphae for the 
most part become intercellular (PL III, Fig. 5 a). Several hyphae (eight 
or more) may frequently be found traversing a single intercellular space 
(Text-fig. 4, a). 
With few exceptions the principal intercellular hyphae pursue a course 
more or less parallel with the long axis of the host-root (Text-fig. 5 ; 
PL III, Fig. 5 A), but cross-connexions between two or more of these main 
Text-fig. 3. Cortical cells undergoing further division as a result of the presence of the endo- 
phyte. a. From a transverse section of Marattia Cooperi , Mre. b. From a longitudinal section of 
A rchangiopteris Heriryi, Chr. et Gies. The cell-contents are not shown, x 200. 
hyphae are not infrequent. From the intercellular hyphae numerous 
branches of limited growth penetrate the walls of the surrounding cortical 
cells. These short hyphal branches ramify repeatedly within the invaded 
cell, where they form peculiar tufts of exceedingly fine mycelial threads. 
Structures of this nature, for which Gallaud (l.c., p. 223 et seq.) has 
proposed the term ‘ arbuscules ’, appear to be characteristic of most endo- 
trophic fungi, and are undoubtedly homologous with the haustoria of the 
Peronosporaceae. The ultimate ramifications of these intracellular branches 
are so fine, and possess such an exceedingly delicate membrane, that even 
under a very high magnification their true form can be distinguished only 
after careful treatment. Judging from the infrequency with which it is 
found, this stage is quickly passed over ; the fine threads of the ultimate 
branches soon lose their individuality, and finally become transformed into 
structureless, granular conglomerations (‘ sporangioles ’ of Gallaud, 1 . c., 
