ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 903 
sporophylls, as the morphological nature of these organs is somewhat doubtful, in 
view of their remarkable variations in position, in various Calamarian fructifications. 
The sporangiophores in each verticil are usually about half as numerous as the 
bracts of a sterile whorl (see Plate 73, photograph 13). We have found 6, 7. and 8 in 
different whorls, and the number seems to have varied even in the same specimen. 
Six seems to be the most frequent number. It is evident that the sporangiophores 
cannot always have been exactly half as numerous as the bracts, for the number of 
the latter may be uneven (see photograph 12 on Plate 73), nor have we seen any 
sterile whorl with as many as 16 bracts. 
The sporangiophores, unlike the bracts, do not alternate with one another in suc- 
cessive whorls, but are placed one above the other, in vertical rows (see Plate 73, 
photograph 11). Hence, it is evident that their position can bear no constant 
relation to that of the bracts. 
Each sporangiophore consists of a stalk or pedicel, having a peltate expansion at its 
free end. The pedicel is broadest at its base (see Plate 73, photograph 13, and Plate 
81, fig. 29). 
The peltate expansion of the sporangiophore bears four sporangia, which are 
attached to its underside, at the extreme edge. A tangential section of the strobilus 
constantly shows the four diagonally placed sporangia grouped around the pedicel of 
each sporangiophore (see Plate 73, photograph 11, Plate 81, fig. 30). 
The whorl of sporangiophores, with their sporangia, appears to have almost filled 
up the space between two successive verticils of bracts. 
The short sketch which we have given of the general morphology of the strobilus is 
sufficient to show that, so far as the sporangiophores are concerned, Calamestachys 
shows a general resemblance to Hquisetum, as has often been pointed out before. 
The smaller number of sporangia on each “ peltate scale” is not a difference of much 
importance. 
The alternating verticils of sterile bracts are, however, without an analogue in 
Equisetum, unless indeed we regard the “annulus” in the latter genus as repre- 
senting a single whorl of bracts at the base of the strobilus. It is evident that 
Calamostachys, and indeed all the allied fructifications, were more highly differen- 
tiated than those of existing Hquiseta. 
We will now proceed to consider the structure of C. Binneyana in detail, beginning 
with that of the axis. 
2.—Structure of the Amis. 
The axis of the strobilus is in all cases traversed by a central cylinder, or stele,* 
which consists of a pith, surrounded by a ring of vascular bundles. Two distinct 
* We adopt the convenient term, introduced by M. van Tincuna, for the whole central cylinder, 
whether of a root or stem, including pith (if present), vascular bundles, interfascicular tissue, and 
MDCCCXCIV.—B. 52 
