SHOWING STRUCTURE, FROM THE RHYNIE CHERT BED, ABERDEENSHIRE. 607 
The sporangium represented in fig. 10 is peculiar in that the epidermal layer of 
its wall is not sharply distinguished from that of the stalk. A firm tapetal 
layer seems to be completely wanting, though the soft tissues of the wall 
are well preserved. This peculiar sporangium widened out gradually from the 
stalk without any constriction at the base. The sporangial cavity is partly filled 
with mature spores. 
Another small sporangium (fig. ll) was even more remarkable. The group of 
spores, still arranged in tetrads, is surrounded by a thick wall, which has neither a 
definite tapetal layer nor a characteristic thick-walled epidermis. The ill-preserved 
epidermis is bounded by a cuticle which is ridged like that of adjacent vegetative 
stems of R. Gwynne-Vaughani ( cf. Part I, PI. VI, figs. 31, 36, p. 769). 
The two sporangia last described, which clearly belong to R. Gwynne-Vaughani , 
suggest a less differentiated condition in which spores were formed within the end of 
a stem without this being modified into a definite sporangiun. It is of interest to 
find this type of sporangium co-existing in the same species with a more specialised 
type, provided with a tapetal layer and a specially constructed and thickened 
epidermal layer. There is no evidence, however, that any of the sporangia of* this 
plant had a definite dehiscence. 
The spores of R. Gwynne-Vaughani in the sporangium in fig. 11 were still 
associated in tetrads (fig. 12). Other mature spores from the sporangium in fig. 9 
are represented in fig. 13. The fully mature but not shed spores of this species 
measure about 40 p in diameter. 
Phynia major, n.sp. (Pis. II and III.) 
1917. Rhynia Gwynne-Vaughani , Kidston and Lang (pars), Trans. Roy. Soc. Edin., vol. li, pi. i, fig. 1 ; 
pi. iii, figs. 11-12; pi. iv, figs. 13-19; pi. v, figs. 21-22; pi. vi, fig. 37; pi. ix, figs. 62, 
64-69 ; pi. x, figs. 70, 71, 76-78. 
The figures quoted above, and the descriptions in Part I based upon them, give 
the structure of all the regions of the plant — rhizomes, stems, sporangia — of R. 
major. It has been already pointed out that the differences distinguishing this 
species from R. Givynne- Vaughani are mainly those of size and of minor details. It 
is necessary to consider the new species a little more fully, however, in order to bring 
out clearly the nature of these differences. 
The remains of R. major so far found do not give any such picture of the habit 
of the plant as a whole as the specimen figured in Part I, PL II, fig. 5 did for 
R. Gwynne-Vaughani. The greater diameter of the stems, as shown in PI. I of 
Part I, suggests that R. major was a larger plant throughout, and this is supported 
by the large size of the sporangia. We have, however, no direct evidence of the 
height this species attained. 
We have nothing to add to the description of the rhizomes of R. major given in 
Part I, except to record the occurrence of similar though less perfect examples, 
