866 DR R. KIDSTON AND PROF. W. H. LANG ON OLD RED SANDSTONE PLANTS 
represented in fig. 79. In this case also it is only possible to point out the resem- 
blance to some Protococcacese and Cyanophyceae, for the peculiar appearance might 
result from partial decay of a group of fungal spores preceding the preservation. 
Though placed for convenience with the fungi, these specimens must be regarded 
as incertse sedis. 
The peculiar spore-like body represented in figs. 80 a, 80 b, occurred in the decayed 
cortex of a stem of Asteroxylon. The brown wall of the spore on surface view 
(fig. 80 a) showed a reticulate thickening. In section the wall appeared covered by 
short thin-walled tubes standing at right angles to the surface (fig. 80 b). The 
bases of these tubes seen in optical section give the appearance of the reticulum 
in the first figure. 
The fungi so far described have, as a rule, been situated within the decaying 
tissues of portions of the vascular plants. Some of them, especially resting-spores, 
are also met with isolated in the matrix by decay of the surrounding tissues, while 
type 10 appears to have grown and increased in amount in the amorphous matrix 
adjoining decaying stems. Hyphee of fungal mycelium are also met with, branching 
in the matrix in a fashion that indicates their growth through it rather than their 
isolation by decay of portions of the vascular plants. No specially characteristic 
forms of fungi have, however, been met with in the matrix only. 
The very well-defined dark spores of medium size and distinctly borne on hyphse, 
shown in fig. 81, occurred in the peaty matrix. Somewhat similar specimens have, 
however, been noted within the decaying tissues. 
( b ) Distinction and Description of Species of Fungi. 
The examples described and illustrated above fairly represent the forms of fungi 
which have come to our notice in studying sections prepared from the Rhynie chert. 
A survey of them shows that they all consist of branched mycelium bearing terminal 
or intercalary vesicles or resting-spores. The mycelium is usually and typically 
non-septate. The hyphse show a considerable range in diameter, and the vesicles 
or resting-spores differ widely in size and in the characters of their wall. It must 
remain an open question to what extent the form-types distinguished above are 
specifically distinct. The differences in thickness of. hyphse and in size of resting- 
spore may have been affected by the conditions of life, and perhaps by the occurrence 
of the fungi in parts of different plants. It does not appear advisable to multiply 
species or specific names on the imperfect differential characters afforded by fungal 
remains without any reproductive organs other than chlamydospores. On the other 
hand, some of the forms are evidently distinct and maintain their characters 
wherever met with in the deposit. Some are further of interest on account of 
their regular association with the remains of particular plants or parts of plants. 
We propose to adopt a middle course and, while not giving names to all the forms 
recognised above, to distinguish some of the most characteristic of these as species 
