HA R D WICKE ' S S CIE NCR- GO SSI P. 



229 



tended across. The stem of a calamite was thus 

 composed of three divisions, viz, bark, woody zone 

 and fistular pith, the most important of these being 

 the woody zone. This zone was formed by a series 

 of woody wedges which varied in number from eleven 

 to sixty or more, according to the size of the plant — 

 the wedges being composed of from fourteen to 

 eighteen lamina; or rows of vessels. In transverse 

 and longitudinal sections these vessels closely re- 

 semble those of the fossil pines of the coal-strata ; 

 the only difference being that in the calamites they 

 are arranged in a different way, and their markings are 

 different, from what obtains in the fossil pines. The 

 nodes were formed by a series of arches which extended 

 across the young plant in a rather complicated manner 

 and gave off the leaves in verticels. 



It is generally supposed that the branches were 



Sandstone casts of young calamites are very liable 

 to break up into segments at the joints, in digging 

 them out of the matrix. This is owing to the fact 

 that in the young calamites the arches of woody 

 tissue crossing the nodes were thicker and more 

 compact than they appear to have been in the older 

 plants, so that during the process of fossilisation when 

 their interiors became filled with sand or other 

 material and their woody cylinders became converted 

 into coal, a thin layer of coaly smudge was formed 

 betv/een each joint or node, thus preventing that 

 cohesion of the joints which obtains in older plants. 



It is very singular that a complete stem of a 

 calamite should be so seldom met with, yet such is 

 the case ; not one specimen in a dozen shows any 

 trace of the bark. When it does occur it is seen to 

 consist of a loosely formed parenchyma, and there is- 



Fig. 136 — Transverse Section of Calamite. X lo diameters. 

 (From a young specimen in the Author's cabinet.) 



Fig. 137. — Calamite ; the young specimen with the bark 

 on. (From the Author's cabinet.) 



also arranged in verticels, at each node after the 

 manner which obtains in the horsetails, but recent 

 researches have shown that such was not the case, 

 except in very young plants. The branching took 

 place at the nodes, but probably at irregular intervals, 

 each branch being articulated to the stem, and taking 

 its i;ise in one of the small orifices at a node, rapidly 

 increased in size in passing through the thick bark, 

 so that upon or shortly after emerging to the surface 

 it was nearly as thick as its parent stem. Some of 

 my sections show this peculiar mode of branching 

 remarkably well. These facts explain the curious 

 appearance of the end of an ordinary calamite, 

 where it begins in a small point and rapidly increases, 

 so that in a few inches it attains its maximum size, 

 while the large number of nodes which are there 

 crowded together in so short a space, show how 

 firmly it was attached to the bark of its parent stem. 



no wonder that such a delicate corky structure 

 should be so infrequently preserved in a fossil state. 

 To me it is still more singular, that the smooth hard 

 woody cylinder should have been so rarely preserved 

 as a sandstone or ironstone fossil. It is very pro- 

 bable that the following explanation of this point 

 may be the correct one. " The cast of the interior 

 which in time became harder than the vascular 

 tissues of the stem acted upon as it was by the water 

 that saturated the deposit, resisted more successfully 

 the pressure of the superincumbent deposits, which in 

 compressing the stem produced on its outer surface 

 a counterpart of the furrows and constrictions of the 

 internal cast." ["The Botany of a Coal-mine," by 

 WilhamCarruthers, F.R.S., P.S. Review, July 1876.],, 

 We frequently find sandstone casts of calamites 

 of large diameter — sometimes over six inches. 

 If these merely represented the "casts" of the 



