832 DR R. KIDSTON AND PROF. W. H. LANG ON OLD RED SANDSTONE PLANTS 
some new facts regarding the various plants which have come to light since the 
descriptions were published. 
Rhynia Gwynne-Vaughani (PL I, fig. l). 
We have some direct evidence as to the mode of growth, height, and general habit 
of this plant. The block represented in Part I, fig. 5, in which the plants were 
preserved standing erect as they grew, shows the crowded, rush-like growth of the 
erect, tapering stems. These could be traced for a length of 13 cm., but were 
incomplete. In the reconstruction the plant is represented as about 17 cm. high, 
which may fairly be taken as about the mean height. Since, however, stems have 
been met with of 3 mm. diameter, while the stems in the specimen in Part I, fig. 5, 
were of the more usual diameter of 2 mm., the plants of Rhynia Gwynne-Vaughani 
probably attained a somewhat greater height than is shown in the reconstruction ; a 
height of 20 cm. was suggested in the diagnosis. 
The aerial stems tapered from a diameter of two (to three) millimetres at the 
base to about one millimetre. Examples of dichotomous branching have been met 
with sparingly. We have represented the sporangia as terminating some of the 
tapering stems, and take the size of the sporangia, from the few specimens seen, as 
about 3 mm. (or slightly more) in length by 1 to 1'5 mm. across. The rhizomes, of 
which only a few good specimens have been seen, were stem-like and about the same 
diameter as the aerial stems ; they bore rhizoids on the lower side. 
Most specimens of Rhynia Gwynne-Vaughani have shown the structures which 
we have spoken of as hemispherical projections. The size and distribution of these are 
best shown in figs. 7 and 8 of Part I ; these represent pieces of stem, about 5 mm. in 
length, and bear on the surface turned towards the observer five and three projections 
respectively ; there are no projections on the piece of stem in fig. 6. The projections 
are somewhat longer in the direction of the length of the stem, and have thus an oval 
outline ; they are about ^ mm. long. These projections are simply indicated by 
dots in the reconstruction. The larger or smaller adventitious branches, which 
occupied the position of some of the hemispherical projections, are also represented 
in this. 
Some further particulars with regard to the hemispherical projections may 
conveniently be given here. Their general structure was illustrated in Part I, 
figs. 50 and 51. It was there shown that the projection is a localised pro- 
tuberance of small cells referable to divisions in the epidermis and the layers 
immediately below this, and bursting the thick cuticle. Both a vertical elonga- 
tion of the cells and their septation by thin walls are concerned in the localised 
growth. A similar longitudinal vertical section of another projection is given here 
(PI. Ill, fig. 5). 
To this we have now to add the fact that in a number of examples the projection 
has been clearly seen to have formed more or less directly underneath a stoma. 
