33 
strobilus can scarcely be distinguished from that of some living Lycopodia, 
except in the difference of size. 
Respecting Calamites, Mr. Carruthers says, "Few fossils have been 
more misunderstood than the set of plants to which the name of Calamites 
is given. One of the least errors regarding them was that which placed 
the stem upside down, and made the cylindrical roots its leaves. The 
branchlets and foliage have been referred to the genus Astcrophyllites, 
supposed to be independent aquatic plants, and the fruits form the genus 
Volkmannia. Calamites usually exhibit an apparently furrowed and 
jointed stem, somewhat resembling the recent Equisetaoese. The few 
specimens that have been found with the internal organisation of the stems 
preserved, show a structure differing from what had been assumed to be 
that of Calamites, and have been constituted into the genus Calamodendron. 
The stem of Calamites was formed on a different plan from that of 
Lepidodendron. The axis consists of a considerable mass of cellular tissue. 
This is surrounded by a solid cylinder of wood, formed entirely of scalariform 
vessels, these formed constrictions at regular intervals ; beyond the woody 
cylinder there was an epidermal layer of parenchyma, which is less seldom 
preserved even than that of the interior. When the stems were thrown 
down the cellular portions were generally completely destroyed, and the * 
space occupied by the axis was filled by the clay or sand in which the plant 
finally rested. In this way a cast of the interior was made, which in time 
became harder than the vascular tissue of the stem, and the pressure of the 
superincumbent deposits flattened and compressed the woody cylinder, pro- 
ducing on its upper surface a counterpart of the internal cast with its 
furrows and constrictions. The stem somewhat rapidly contracted at the 
base, the nodes shortening and giving off cylindrical roots which spread 
laterally through the soil. The main stem was simple, but at intervals gave 
off whorls of slender branches, and these again bore branches or leaves also 
arranged in whorls, each whorl containing from ten to twenty leaves of a 
linear acuminate form. The fruit was composed of whorls of scales 
alternating with, and protecting whorls of sporangium-bearing spines. It 
was borne at the end of the primary branches, or in whorls around them 
and was composed of a shortened axis, with the leaves specially developed. 
The strobilus consists of protecting scales fifteen in a whorl, the scales of 
each whorl being opposite to those in the others : between the scales is a 
whorl of five short spines, each supporting four flask-shaped sporangia 
arranged perpendicularly on the axis, the one directly over the other." 
