440 COENOPTERIDEAE [CH. 



that of other species, and he suggests the institution of a new 

 genus. 



Botryopteris ramosa (Williamson). Fig. 306. 



This species, which bears a close resemblance to Botryopteris 

 hirsuta, was originally described by Williamson from the Lower 

 Coal-Measures of England as Rachiopteris ramosa^, the specific 

 name being chosen on account of the numerous and crowded 

 branches given off from the main axis. The section shown in 

 fig. 306, A, illustrates Williamson's description of the stem as 

 being "always surrounded [when seen in transverse sections] 

 by a swarm of similar sections of the large and small branches, 

 though of varying shapes and sizes." The stele is composed of 

 a solid and more or less cylindrical rod of xylem tracheae of 

 the reticulate type surrounded by phloem (figs. A and D) : one 

 or more internal groups of smaller protoxylem elements occur 

 in an approximately central position (fig. A, px). The stele is 

 in fact endarch like those of Selaginella spinosa and Tricho- 

 manes reniforvie, a feature which, as Tansley" believes, probably 

 entitles the vascular axis to be considered a primitive form of 

 protostele. In the specimens represented in fig. 306 the phloem 

 and inner cortical tissues were almost completely destroyed 

 before petrifaction. The thick-walled outer cortex bears at its 

 periphery numerous multicellular hairs. Some of the xylem 

 strands given off from the stele no doubt supplied adventitious 

 roots, but in most cases the outgoing branches are leaf-traces 

 and the numerous sections of axes of different sizes seen in 

 fig. A point to a repeated subdivision of the crowded fronds. 

 The structure of a petiole is shown in figs. C and D. As seen 

 in fig. C, the oval vascular strand has three protoxylem groups, 

 px, on its flatter side ; a well-defined epidermal layer is shown 

 at e in fig. C. 



Fig. B shows at a a section of a leaf-axis in the act of 

 branching and the row of branchlets at b represents a further 



1 Williamson {9V) A. p. 261. The two species described by Williamson 

 as Rachiopteris hirsuta and R. ramosa were first identified as Botryopteris by 

 Scott in 1898 (British Assoc. Report, Bristol Meeting, p. 1050). 



2 Tansley (08) p. 15. 



