892 DR R. KIDSTON AND PROF. W. H. LANG ON OLD RED SANDSTONE PLANTS 
F 116. It is of interest, as indicating a recurrence of similar, probably submerged, 
conditions at these levels, that the algal remains described under the name Algites 
Cranii occur at the same two levels in the chert-band. 
The fragments of Nematophyton have only been met with at one spot in the clear 
peaty matrix of Bed A"l, some little distance above the level where the felt of 
Schizophyta No. 2'and the remains of Algites Cranii occurred. 
It is noteworthy that Crustacean remains were most abundant in the Rhynia 
Gwynne-Vaughani peat of the lower region of Bed A"l, where the last-named plants 
were found. 
6. Remarks on the Nature, Conditions of Accumulation, and 
Preservation of the Rhynie Deposit. 
In the first of this series of Memoirs (Part I, p. 764) some remarks were made 
and a general view expressed regarding the nature and origin of the silicified chert- 
band found at Rhynie. The accumulation of beds rich in plant-remains and free 
from admixture of mineral particles was compared to the growth of a modern peat. 
The fact that the peat is interrupted at intervals by more or less regular sandy 
layers was interpreted as indicating frequent flooding of the surface. The silicifica- 
tion was regarded as due to a final saturation of the peat-bed, or rather the system 
of peat-beds and sandy layers, by water with silica in solution, derived from 
fumaroles or geysers. 
As a general hypothesis which covers the main facts this may stand. Now that 
the plant-remains have been examined throughout a complete vertical section, it is 
possible, however, to amend and amplify this view in some points of detail. 
The outstanding features of the Rhynie bed as shown in the section described 
above may, in the first place, be summarised, since it is from a consideration of them 
that any more detailed indications as to the conditions of accumulation of the deposit 
can be expected. It has been seen that — 
(а) The structural characters of Rhynia and Asteroxylon , especially the presence 
of stomata in the epidermis from the base of the stem upwards, indicate that the 
growth of these plants was not truly aquatic. The soil may, of course, have been 
swampy or saturated with water. On the other hand, Hornea might have grown in 
shallow water, though there is no direct evidence for this. 
(б) There are indications of growth in situ of Rhynia Gwynne-Vaughani in the 
basal bed, of Asteroxylon in the sandy layer covering the Hornea peat of Bed A"l, 
and of the Hornea in the same region. There is also evidence for the growth in 
situ of Rhynia major in the peat of some of the upper beds. These various indica- 
tions justify us in regarding the peat-layers as largely formed by the growth of 
plants on the spot ; the carriage of remains from the near neighbourhood and 
their accumulation, possibly under water, is not excluded in the case of some of 
the beds.- 
