X] CALAMOSTACHYS. 353; 



of a sterile whorl, and the members of the several fertile whorls 

 are superposed and not alternate. Each member has the form 

 of a stalk or sporangiophore given off at right angles from the 

 cone axis ; this is expanded distally into a peltate disc bearing 

 four sporangia attached to its inner face. In fig. 94 we can only 

 see the basal portions of the sporangiophores, which are shown 

 in the upper part of the sketch as pointed projections, Sp, from 

 the cone axis. Each sporangiophore is traversed by a vascular 

 strand which sends off a branch to the base of a sporangium 

 (fig. 95, A, t). 



The axis of the cone is occupied by a single stele, usually 

 triangular in section ; the stele consists of a solid pith of 

 elongated cells surrounded by six vascular bundles, two at 

 each corner. A somewhat irregular gap marks the position 

 of the protoxylem of each strand, and portions of spiral or 

 annular tracheids may occasionally be seen in the cavity. 

 These cavities, which may be spoken of as the carinal canals, 

 disappear at the nodes, where there is a mass of short reticu- 

 lately pitted tracheids, as in a Calamite stem. Vascular bundles 

 pass upwards in an oblique direction from the central stele 

 to supply the bracts, each of which is traversed by a single 

 strand of tracheids. The coherent portion, or disc, of each 

 sterile whorl consists of sclerenchymatous elements towards 

 the upper surface, and of parenchyma below. The pedicel of 

 the sporangiophores consists of fairly thick-walled cells traversed 

 by a single vascular strand, and the peltate distal portions are 

 made up of parenchymatous cells arranged in a palisade-like 

 form at right angles to the free surface of the sporangiophores. 

 The vascular strand of the pedicel forks into two halves just 

 below the peltate head, and these branches again bifurcate to 

 send a branch to each sporangium. The four sporangia of 

 each sporangiophore are attached by a narrow band of tissue 

 to the shield-shaped distal expansion (fig. 95, A). 



In a tangential section of a cone, such as the lower portion 

 of fig. 94 and in fig. 95, B, the sporangiophores present the 

 appearance of narrow stalks (fig. 95, B, a) in the middle 

 of a cluster of sporangia, and the latter appear more or less 

 square in outline. The wall of a sporangium is made of a 



a. 23 



