OF CALAMITEAN STROBILUS. 251 



peduncles given off from the central axis. Each of these 

 has an average breadth of about ^^^ of an inch. It consists 

 chiefly of cellular tissue, the cells being of various sizes. In 

 the ring immediately investing the pith the cells are the 

 largest, being from about ^-^ to ^-ou of an inch in diameter. 

 In the centre of each peduncle they are about -g-J^ of an inch 

 in diameter. At d d are two pores, which are sections of 

 two canals, running the entire length of the axis of the stro- 

 bilus, and which serve in an important manner to identify 

 homologous parts in different sections. These canals have 

 a diameter of 4^ of an inch, and the cells immediately 

 surrounding them range from about yi^ro to tbVo of an 

 inch in width, these being much smaller than the rest. 

 The dark and dense patches, e e, 1 believe mark the posi- 

 tion of some important bundles of reticulated vessels to 

 which I shall again have to refer. At /// are three of 

 the pyriform spaces separating the primary peduncles. The 

 transverse section of each of these is broadly ovate at its 

 inner extremity, and acuminate in the opposite direction. 

 On each side of this acuminate portion, and separated from 

 it only by a very thin film of oblong cells, is the ovate 

 basis of a smaller, but otherwise similar, space (g), at the 

 peripheral end of which is a patch of tissue {h) somewhat 

 denser than the rest, and which marks the starting-point 

 of a spore-bearing peduncle or sporangiophore, which as- 

 cends almost vertically into the substance of the strobilus. 

 These sporangiophores are twenty in number, or double 

 that of the primary peduncles. The remainder of this 

 section consists chiefly of coarse cellular tissue, with the 

 exception of the darkly shaded portions, i i, which are 

 masses of spores. Owing to the peculiar inflections of 

 the bractigerous disk given off from each node, no one 

 continuous horizontal section can be made through its 

 entire plane, as will readily be understood on reference to 

 the restored vertical section of the strobilus, fig. 13, where 



