604 DR R. KIDSTON AND PROF. W. H. LANG ON OLD RED SANDSTONE PLANTS 
The difficulty of sharply distinguishing particular fragments of these two plants 
is in no way inconsistent with the opinion we have been led to form, that they are 
distinct but closely allied species. Their comparative study is assisted by certain 
beds or loose blocks containing the remains of only one or the other species. The 
difference in size of the two plants will be evident on comparing the block of chert 
represented of natural size in PI. I, fig. 1, with the figs. 2 and 5 on PI. II of our 
former paper. The peat in fig. 1 is composed of stems of R. major, many of which 
have a diameter of 5 mm., while the stems of R. Gwynne-Vaughani in figs. 2 and 5 
are about 2 mm. in diameter. 
Although we were dealing with mixed material of two species, which we now know 
separately, the description of the plant and its differentiation into rhizome, stems, 
and sporangia given in Part I holds good for both species of the genus Rhynia. It 
has only to be qualified by recognising the specific differences to be dealt with below. 
It will be convenient at this stage, however, to review the illustrations to our former 
paper and to indicate which belong to R. Givynne-Vaughani and which to R. major. 
AIL the figures on PI. II are of R. Gwynne-Vaughani, as are also figs. 6-10 on 
PI. Ill, fig. 20 and figs. 23-30 on PI. V, all the figures on PL VI except fig. 37, and 
all the figures on Pis. VII and VIII. The sporangium in figs. 63 and 63a on PI. IX 
is the only one figured that belongs to this species. Pigs. 72-74 on PI. X are small 
stems of this species. A survey of the figures named shows that the general habit 
and size of R. Gwynne-Vaughani, the external features of the stems, the details , of 
structure of the stems, the hemispherical projections and the occurrence in their 
place of adventitious branches, and the sporangium were represented. The trans- 
verse section of a stem in Dr Mackie’s paper,* which was the first figure of Rhynia 
published, also belongs to this species. 
To R. major, on the other hand, we now refer fig. 1 on PI. I, showing a block of 
the chert with the stems of natural size ; all the figures of rhizomes on PI. IV (figs. 
13-19), with the details in figs. 11 and 12 of the preceding plate; the large stems 
in figs. 21 and 22 t of PI. V ; the outer cortex and stoma in fig. 37 on PI. VI ; the 
large sporangia in figs. 62 and 64-69 on PI. IX ; the spores in figs. 70 and 71 of PI. X ; 
and the partially decayed stems in figs. 76-78 of the same plate. J Consideration 
of these figures will ' show that the rhizomes, stems, and sporangia of R. major 
were represented, though the detailed account of the structure of the stem is 
based on R. Gwynne-Vaughani. On the other hand, all the rhizomes described 
and figured in Part I are of R. major, and the description of the sporangium is 
mainly based on this species. 
The rhizomes figured on PI. IV of Part I all occurred in one block of silicified 
* Trans. Edin. Geol. Soc., vol. x, 1913, pi. xxii, fig. 5. 
t The magnification of figs. 21 and 22 on PI. V of Pt. I was erroneously given as 20 diameters. These stems are 
magnified about 14 diameters. 
| To complete this survey of the illustrations to Part I, it should be stated that the poorly preserved specimen in 
fig. 75 of PI. X does not belong to Rhynia, hut to Asteroxylon. 
