CALAMARIEAE. 305 



Further, the course of the strands in Calamarieae appears to deviate in 

 not unimportant points from that hitherto assigned to Equisetae, as may 

 be gathered from certain anomalies in the sculpture of the casts which must 

 be considered by-and-by. On this point there is scarcely anything to be 

 said in the absence of investigations into the details of the subject. I may 

 mention however that I have seen a section in the British Museum, in the 

 node of which several adjacent xylem-strands of the successive internodes 

 instead of alternating lay exactly one on another. The upper trace-strand 

 divides into two limbs, which diverging first of all and anastomosing laterally 

 with neighbouring strands, afterwards converge again and unite to form 

 the lower trace-strand. In the mesh thus formed, which breaks the direct 

 continuity of the strands, there was always to be seen the transverse section 

 of an emerging bundle, or at least the trace of the particular node. 



Lastly, before going on to speak of casts of Calamitae it will be necessary 

 to notice the genus Astromyelon, about which very different views have 

 been expressed in recent times. This genus was founded by Williamson l 

 on remains which showed in their transverse sections the characters of 

 Arthropitys, with the exception of the intercellular cavity in the primary 

 bundle ; and in it he now places several of the transverse sections 2 which 

 he had himself before named Calamites, and makes its most important 

 character to be {he absence of stem-nodes bearing whorls. It is also said 

 that the parenchyma of the medullary cylinder is usually though not 

 invariably preserved. Meantime remains of peculiar stems with spongy 

 lacunose rind and with the medullary cylinder filled with parenchyma were 

 discovered by Hick and Cash 3 in Halifax, and were described as Myrio- 

 phylloides Williamsonis ; but they were subsequently re-examined by 

 Williamson 4 and united with Astromyelon, the peculiar feature of the 

 rind being added to the characters of the genus. However, Hick and Cash 5 

 have at once raised objections to this identification. That the transverse 

 section of the wood-body of Myriophylloides does really show a picture 

 different in not unimportant points from that of Arthropitys, I have been 

 able to satisfy myself by inspection of sections obtained from Mr. Cash 

 himself 6 ; but it is useless to discuss the question till we have more in- 

 formation respecting the nature of the longitudinal sections. 



The characteristic structure of the rind depends on the presence of a 

 simple girdle of wide intercellular spaces in the middle of the rind, which 

 become broader and wedge-shaped towards the outside, and which, evidently 

 schizogenetic in origin, are separated from one another by narrow radial 

 plates of tissue from two to a few cells in breadth. But a structure of 



1 Williamson (1), IX, p. 319. a Williamson (1), I, t. 25, f. 16, and t. 27, f. 39. 3 Hick 



and Cash (2). 4 Williamson (1), XII, p. 459. 5 Hick and Cash (1). 6 Williamson 



(1), xn, f. 5. 



X 



