862 DR R. KIDSTON AND PROF. W. H. LANG ON OLD RED SANDSTONE PLANTS 
tudinal rows of vesicles or spores in the cortex of stems or occupies a considerable 
area of the cortex. 
The hyphae are about 4 or 5 m in thickness, and the vesicles about 40 n in 
diameter. 
Fungus No. 11. (Figs. 42 and 43.) 
The fungus which we place here resembles the preceding Fungus No. 10 in 
miniature. It is not impossible that with further growth it may have come to 
resemble it more closely. It is represented in figs. 42 and 43. This fungus has 
been met with most commonly in decayed stems of Rhynia Gwynne-Vaughani, but 
also occurs in other plants. Most frequently it appears as relatively small masses 
of fine hyphae bearing small vesicles (fig. 42). As the latter figure shows, these 
masses often appear as if they had been at first defined and enclosed by single cells 
of the tissue and had burst out from them. It sometimes occurs in the region of 
cells with dark contents immediately below the outer cortex of Rhynia (fig. 43), but 
may be situated much more deeply, and even close to the stele. In some cases the 
group of fine hyphae of this fungus appears to have originally occupied and grown 
out from a resting-spore of Fungus No. 2. 
Fungus No. 12. (Fig. 44.) 
This form has much in common with that described as Fungus No. 10. It 
occurred, as shown in fig. 44, in somewhat decayed stems of Rhynia Gwynne- 
Vaughani, but at a slightly higher level of Bed A" 1 . The moderately fine hyphse 
enlarge into thin-walled vesicles, but the enlargement is usually a gradual one, so 
that the vesicles are pear-shaped rather than spherical. Their diameter measured 
across the widest part is rather greater than in the case of the type 10, measuring 
about 60 .a. 
Fungus No. 13.* (Figs. 45-47.) 
The specimen represented rather inadequately in figs 45-47, owing to the thick- 
ness and opacity of the section in which it occurred, we owe to the courtesy of 
Mr John B. Simpson. The fungus was present in a decayed stem of Rhynia Gwynne- 
Vaughani. It occurred in small oval patches, and appeared as if bursting through 
the cuticle or epidermis of the stem ; the distribution might also be explained by 
the patches occupying .the site of thin-walled hemispherical projections that had 
decayed (fig. 45). The prominent structures of each patch of fungus are hyphae 
radiating outwards and dilating into thin-walled vesicles. Even the larger vesicles 
are not divided by a septum from the hypha. The vesicles may be 100 u in diameter, 
but smaller and larger specimens occur in the same patch. Fig. 46 represents one 
patch of fungus, while a few of the vesicles are shown more highly magnified in 
fig. 47. 
* Named Palseomyces Simpsoni below (p. 869). 
