860 DR R. KIDSTON AND PROF. W. H. LANG ON OLD RED SANDSTONE PLANTS 
resting-spores like Fungus No. 2, it is not improbable that we have here a similar 
fungus in an earlier or different condition of development. On the other hand, it 
presents resemblances to the following type, in which the vesicles have never been 
seen to pass into thick-walled resting-spores. 
Fungus No. 7.* (Figs. 20-28.) 
This fungus occurs characteristically between the cells of the inner cortex of 
many of the rhizomes of Asleroxylon, and in the axes intermediate in structure 
between rhizomes and stems. The region occupied is usually more or less decayed, 
while the fungus seems to avoid the outer cortex and phloem. The general distri- 
bution of the fungus was evident in figs. 16 and 22 of Part III. 
Fig. 25 on Plate III shows the relation of the fungus to the inner and outer 
cortex and its general appearance. It consists of stout and fine hyphse and vesicles. 
The intercellular position of the hyphae is shown in fig. 26. Fig. 27 and fig. 20 
show the hyphae and vesicles in more decayed tissue of the inner cortex. The 
fungal hyphae are non-septate, only an occasional transverse septum having been 
seen. The hyphae are abundantly branched (fig. 21), and sometimes connected by 
anastomosing branches (fig. 22). The branches are sometimes recurved (figs. 20, 28). 
The ends of many of the finer branches expand as oval or spherical thin-walled 
vesicles which are usually not cut off by a septum from the cavity of the hypha 
(figs. 23 and 24). The walls of the vesicles are not specially thickened, and do 
not show any tendency to separate into layers or to give the appearance of a 
double contour. 
The fact that, as a rule, when the cell walls of the tissues are preserved the 
fungus is intercellular has been emphasised above. Fig. 28 shows a superficial 
cell of the outer cortex of the rhizome in fig. 25 which has been entered by the 
fungus, that in this specimen was growing on the outer surface of the rhizome ; 
a vesicle has formed on the fungus within the cell. Both the position and the 
behaviour of the fungus in this case are, however, exceptional. 
The figures show the range in diameter of the non-septate hyphse and also of the 
vesicles. This makes it impossible to state a definite characteristic size. It may 
be generally said that the hyphse range in diameter from about 4 n to 20 n, while 
the vesicles attain a size of about 80 n. 
Fungus No. 8.t (Figs. 29-35.) 
This fungus is present in many of the protocorm-like rhizomes of Hornea , 
extending also into the region of the stem attached to the rhizome. It seems to 
be almost always present in these positions in certain beds of the peat, while it is 
completely absent from the same portions of Hornea in other beds. 
The non-septate hyphse are stout (about 10-15 n) and of a dark colour (fig. 32). 
* Named Palxomyces Asteroxyli below (p. 869). f Named Palxomyces Hornem below (p. 869). 
