XXXir] CALAMOPITYS 193 



Calamofitys annularis (Unger)^. 



This species, originally assigned to the genus Stigmaria, has 

 a more strongly developed primary vascular system and there is 

 a more decided tendency towards the formation of a continuous 

 zone of primary xylem on the inner edge of the secondary wood ; 

 but where the protoxylem tracheids occur the metaxylem elements 

 form definite strands, like those of C. Saturni. It has been pointed 

 out by. Scott and Jeffrey that there is some evidfcnce of the 

 occurrence of tracheids in the parenchymatous pith of this species, 

 an important feature distinguishing it from C. Saturni and con- 

 necting it with C. americana. Information with regard to the 

 behaviour of the leaf-traces is far from complete, but there are 

 indications that each trace divides into two before emerging from 

 the secondary xylem^. The leaf-traces in the cortex are concen- 

 tric as in C. Saturni. 



Calamofitys americana Scott and Jeffrey. 



This Lower Carboniferous species* from the Waverley shales 

 of Kentucky is represented by portions of stems and leaf-bases 

 and detached petioles. The secondary wood consists of tracheids, 

 30 — 60|i in diameter, with deep and broad rays ; the small pits on 

 the tracheids form 5 — 6 alternating series. Phloem and cambium 

 are very imperfectly preserved. The outer cortex is of the same 

 type as in other species. At the inner edge of the secondary 

 xylem there is a ring of primary xylem strands of mesarch 

 structure composed of rather larger tracheids, 80^ — 120/x in diameter, 

 separated from one another by narrow strips of parenchyma. 

 So far the vascular tissue agrees with that of C. annularis. In 

 the American species the axial region is not a parenchymatous 

 pith but a protostele, consisting of parenchyma and a larger or 

 smaller number of tracheal groups, the number being less in stems 

 with a larger central region. The peripheral strands alone are 

 concerned with the emission of leaf-traces, as in Heterangium. 

 Each primary xylem strand divides into two as it leaves the peri- 

 medullary zone and passes through the secondary xylem as two 



1 Biohter and Unger (56) B. p. 174, PI. x. figs. 1—3; Solms-Laubaoh (96) B. 

 p. 73; Scott (12) p. 1027. 



2 Scott and Jeffrey (14) p. 326. 



3 Ibid. p. 317, Pis. 27, 28, 30, 31. 



s. in 13 



