SHOWING STRUCTURE, FROM THE RHYNIE CHERT BED, ABERDEENSHIRE. 857 
{a) Description of Form-types of Fungi recognised in the Rhyme Peat. 
Fungus No. 1 . (Figs. 1-4.) 
The mycelium of the various types of fungi to be described below will be seen 
to be, as a rule, non-septate. The specimen here described and figured agrees in 
the general characters of the mycelium with some other fungi to be considered later, 
but shows more or less numerous transverse walls in some, at least, of the hyphse. 
It is further interesting in that the hyphse are associated in strands which, as is 
not unusual, occupied the place of the phloem in a partially decayed stem of Aster- 
oxylon ; the stem was cut longitudinally, and therefore shows a strand of hyphse 
on each side of the xylem (figs. 1 and 2). The stout hyphse run on the whole 
parallel to one another, and are branched without any relation to the position of 
the septa. At places the branches form peculiar tangles or knots (fig. 2), but, 
though anastomoses not improbably occurred, there are no indications of clamp- 
connections. The transverse septa, the middle portion of which is often thicker 
and of a darker colour than the outer walls of the hyphse, occur at irregular 
intervals. They were frequent and distinct in the strand seen on one side of the 
stele' (fig. l), while they were present, though less frequent, in the strand on the 
other side (fig. 2). Some of the septate hyphse are shown more highly magnified 
in fig. 3, and some of the non-septate hyphse in fig. 4. The same stem of Aster - 
oxylon also contained the large resting-spores of the fungal type that will be 
next described as Fungus No. 2. The mycelium here described as No. 1 not 
improbably belongs to the fungus which bore the large resting-spores, though direct 
proof of this is wanting. Similar strands of hyphse replacing the phloem in a stem 
of Asteroxylon, associated with the larger resting-spores of Fungus No. 2 in the 
cortex of the stem, are seen in the section represented in fig. 5. 
Fungus No. 2.* (Figs. 5-11.) 
This fungal type is probably the most widely distributed throughout the chert- 
bed. It occurs in fragments of all the vascular plants and is associated with their 
greater or less decay. It is most abundant and characteristically developed in the 
stems of Rhynia major and of Asteroxylon ( cf. Part III, figs. 31, 42, 43, 96). 
In its typical form it has stout hyphse, as well as finer branches. The hyphse 
usually appear non-septate, but in relation to this the remarks under Fungus No. 1 
should be borne in mind. They bear large oval, thick-walled resting-spores, the 
wall of which consists of a number of layers and tends to exhibit a double contour. 
The general appearance of the fungus as it occurs in the decayed cortex of a stem 
of Asteroxylon is well shown in fig. 6, and more highly magnified in fig. 7. In 
this specimen the hyphse were clearly shown, and bore smaller thin-walled vesicles 
as well as the mature resting-spores ; the smaller structures were evidently stages 
* Named Palxomyces Gordoni below (p. 868). 
