OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
77 
ments are exactly identical with those found respectively in Lepidodendroid stems and 
in their Stigmarian roots, as I pointed out in my third memoir *. The close relationship 
between Asterophyllites and Sphenophyllum being thus established upon the sound basis 
of closely identical organizations, the inquiry which suggests itself is, What are the 
real distinctions in their foliage 1 It appears to me that typically there are none. The 
leaf of Asterophyllites has a single midrib ; that of Sphenophyllum has three or more. 
May not each cuneiform leaf of Sphenophyllum be regarded as composed of three or 
more of the divergent leaves of Asterophyllites , which have coalesced throughout the 
greater part of their length, but whose typically separate origin is indicated by the 
number of the teeth usually seen at their broad extremities 1 This explanation further 
accounts for the small number of the leaves usually composing each foliar verticil of 
Sphenophyllum compared with those of Asterophyllites. 
M. Renault’s specimens demonstrate very clearly the existence of a layer of ordinary 
delicate parenchyma within the radiating lines of parenchyma seen in my figures 4, 9, 10, 
& 15. As mentioned in the preceding memoir, I have only caught a glimpse of this layer 
in one or two of my specimens, it having almost invariably disappeared from them, leaving 
a vacant space as in fig. 16, g. This demonstration materially simplifies the identification 
of the layers of the bark in the stems and roots. Thus the layer g in figures 47, 49, & 
57 is identical wfith the innermost parenchyma of Professor Renault ; it corresponds 
with the layer g in figures 9, 10, 11, & 21. In the same way the layer h in these latter 
figures is identical with h in figures 47, 48, 49, & 57. If these conclusions are correct, the 
roots of Asterophyllites have a bark like that of the stems, but almost or altogether 
deprived of the superficial prosenchyma seen in the latter organs ; this layer, however, 
may be regarded as reappearing in the outermost parenchyma (fig. 53, o) of the rootlets. 
I may add that a second copy of my memoir on Volkmannia Dawsoni , which I sent 
to M. Brongniart, has reached him. In a note to M. Renault’s paper, M. Brong- 
niart, acknowledging this memoir, recognizes the important points in which the organi- 
zation of that fruit agrees with that of the structures described by M. Renault, as well 
as those on which it differs, “au moins specifiquement.” — Manchester, February 20, 1874.] 
Description of the Plates. 
The letters of reference in the accompanying memoir have been used to indicate as 
nearly as possible the same structures as in the previous memoirs of the series. The 
letters are not alphabetically continuous, because some of the structures existing in other 
plants are wanting in Asterophyllites ; and I have thought it preferable to omit the letters 
referring to these absent structures, rather than to introduce confusion by employing 
the same letter to represent organs and tissues that were not homologous. The only 
exceptions to this rule will be found in a few of the final letters of the alphabet, which 
have been used for special purposes. 
* Philosophical Transactions, 1872, Part II. p. 307. 
