OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
327 
of the infranodal canals of one internode, whilst in V, we have a few of the similar 
organs from the next inferior internode. The positions occupied by others which 
originally completed this second verticil are indicated by a ring of the small rounded 
scars so commonly seen on the ordinary Calamites (fig. 30, l). There can be no 
doubt whatever that these spokes represent the same parts of the plant as the 
lenticular cell masses, / of figs. 23 and 24. Why these organs continued to be occupied 
by cellular parenchyma in some specimens whilst in others the cellular tissues were 
absorbed when the medullary cells underwent the same fate, the former being thus 
converted into radiating prolongations of the medullary fistular cavity thus produced, 
I cannot determine. The most probable solution is that the two conditions represent 
different species of plants, in some of which the cellular elements of the radii had but 
a transitional temporary use, whilst them function was more permanent in others. 
Some further light is thrown upon these anomalous structures by the specimens 
represented in figs. 26 and 27. These are sections of a large Calamite found by 
Mr. Butterworth, the surface of the node of which exhibited a few deep circular 
depressions, that appeared to have been points from which branches had been detached. 
A transverse section of the structure underlying one of these depressions is 
represented in fig. 26, and a vertical one in fig. 27, both figures being enlarged 
five times. Fig. 26 is a tangential section of the vascular zone of the primary stem, 
the vessels of which are seen at g, g, separated by them numerous accompanying 
secondary medullary rays. These vessels are deflected right and left to allow of the 
exit of a cylindrical mass of parenchyma in which numerous vessels meander in a 
tortuous manner, especially at the upper and lower margins of the cellular area. The 
diameter of this cellular mass is about - 25. Fig. 27 is a radial section through a portion 
of the same Calamite in wdiicli a similar branch is again intersected. At a we have 
part of the medullary fistular cavity, and at & a few of the true medullary cells ; at 
g, g we have the vessels of the vascular zone, which, it will be observed, bend 
outwards from the medulla, both above and below the incipient branch, for min g 
arches across the node, in the way which I have previously described as characteristic 
of them nodal arrangement. At g' , g the vessels are intersected more or less trans- 
versely because of their lateral deflexion to pass round the cylindrical branch, m. 
At its inner extremity, rn', this cellular outgrowth from the medulla is only about 
'033 in diameter, but it increases rapidly hi size as it proceeds outwards, until, at a 
distance of '16 from the point at which it enters the vascular zone, it becomes, like 
fig. 26, enlarged to '25 in diameter. It will be noticed that whilst numerous vessels 
meander amongst the cells of the periphery of the central branch of fig. 26, there is no 
approach to a radiating arrangement of these vessels, or to the formation of a distinct 
vascular cylinder. It is otherwise with fig. 28, which represents a similar section to 
fig. 26, enlarged 30 diameters, from a decorticated Calamite in my cabinet, the 
diameter of which stem is about 1'25, and the thickness of its vascular cylinder 
averages about '25. The primary medullary rays are seen at c, and the intervening 
mdccclxxviii. 2 u 
