874 DR R. KIDSTON AND PROF. W. H. LANG ON OLD RED SANDSTONE PLANTS 
between the occurrence of these fungi and the other cases which at first sight appear 
open to the interpretation of a mycorrhizal association. In all of the latter the 
evidence appears to be much weaker than was the case for the relation of some 
palaeozoic plants to fungi w^hich has been interpreted as probably symbiotic.* Only 
convincing evidence from structural relations is admissible in a physiological question 
such as that under discussion. The appearances in the Rhynie plants do not afford 
such evidence, although they leave open the possibility that a mycorrhiza may have 
been present in the actively living plant. 
2. SCHIZOPHYTA. 
A few remains that belong to either the Bacteria or the Cyanophycese are placed 
together in this section, on account of the impossibility of determining whether 
certain filamentous forms were green or colourless during life. 
Schizophyta No. 1. Unicellular Bacteria. (PI. VII, fig. 85.) 
There is no reason to doubt that unicellular Bacteria were present, often in 
abundance, throughout the partially decayed mass that is preserved in the Rhynie 
chert. The finely granular nature of the matrix, however, renders their recognition 
problematical. This applies even to appearances strongly suggesting colonial masses 
of Bacteria that occur free or coating vegetable fragments or fungal hyphse in the 
peaty matrix. Such appearances closely resemble the mode of occurrence of 
Bacteria in some processes of decay at the present time. 
One illustrative example is represented in fig. 85. The irregularly lobed masses 
there shown occurred in groups in the matrix of a block of the chert that contained 
the algal remains to be described in the following section. They are so like the 
well-defined bacterial colonies or zoogloeal masses that appear when Algae are decay- 
ing in fresh or salt water that they may reasonably be regarded as of this nature. 
The granular character would be due to the unicellular bacteria. For comparison 
unstained colonies of such a recent bacterium are represented to the same scale 
in fig. 86. 
Schizophyta No. 2. (PI. VIII, figs. 87 and 88.) 
The organism represented in figs. 87 and 88 occurred most abundantly in certain 
blocks of the chert at the upper limit of the Rliynia Gwynne-V aughani peat that 
formed the base of Bed A'T. It there formed a loose felt of fine tubular filaments, 
about 2 n in diameter. Groups of fungal spores are entangled in the meshes of the 
felted mass, but seem to have nothing to do with the organism in question. The 
filaments might be slender fungal hyphee, but they have not been observed to branch, 
and their curvature and arrangement is much more suggestive of the growth of one 
of the Trichobacteria than of a fungus. They may represent the sheaths of one of 
* Weiss, Ann. Bot., vol. xviii (1904), p. 255 ; Osborn, ibid., vol. xxiii (1909), p. 605. 
