ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL=MEASURES. 697: 
there is a nearer approach to the original type of “ Astromyelon” than in the specimen 
last considered. We might have added indefinitely to the list of intermediate forms, 
but it is unnecessary to do so. The secondary wood has precisely the same 
structure throughout, and so also has the cortex, wherever it is preserved. 
There is thus no longer any doubt that the forms such as were first grouped 
together in Part XII. of the previous series of memoirs, under the name of 
“ Astromyelon Williamsonis,” really belong to the same plant, and that they consist 
of the roots and rootlets of various orders of branching of Calamites. The only form 
which seems to us strongly to suggest even a specific distinction from the rest, is 
that shown in photograph 4, in which, as already mentioned, the cortex has a 
somewhat peculiar character. 
Renavutr speaks of some of his larger specimens as stolons, not roots. The 
organs to which he applies this name belong, some to Calamites (his Arthropitys), 
others to Calamodendron. The specimens in question are beautifully illustrated in 
his latest work,* and agree perfectly in structure with the larger roots such as we have 
described. We fail to see any reason for applying the name stolon to any of these 
organs. A stolon is a modified stem, and should show the structure characteristic 
of stems. In the organs, however, which ReEnavutr figures, the structure is 
distinctly that of a root, as is especially shown by the centripetal primary wood. 
In the stem of Calamites, as we showed in our former paper, the primary wood is 
centrifugal.t 
Our general results may be summed up as follows :— 
1. The fossils hitherto described under the name of Astromyelon Williamsonis are 
the adventitious roots of Calamites. 
2. Their structure is in all respects that characteristic of roots, as is proved by the 
centripetal primary wood, the alternating strands of xylem and phloém, the endogenous 
mode of branching, and the absence of nodes. 
3. The smallest specimens, with little or no medulla, represent the finest branches 
of the same roots, of which the large medullate forms are the relatively main axes. 
EXPLANATION OF THE PLATES. 
PLATE 15. 
Photographs from the actual sections, taken by the late Mr. W. Kirman, F.C.S. 
Photograph 1. Part of a tangential section through the wood of a stem, showing the 
base of a root, with “ Astromyelon” structure, in transverse section. The 
* Loc. cit., Flore d’Autun,” &c., Part II., Plates 55, 56, 57, 59, and 60. The text of this work 
not having yet been published, we depend entirely on the figures and descriptions. 
+ “Further Observations,” Part I., p. 872. 
MDCCCXCV.—B. 4x 
