SPHENOPHYLLALES 



[CH. 



been found. The cortex consists of slightly elongated rather 

 thick-walled tissue containing secretory sacs. Crowded super- 

 posed whorls of bracts (or sporophylls), usually twelve in each 

 whorl, are borne on the axis and each sporophyll receives a 

 single vascular bundle from one of the vertical ridges of the 

 xylem column (fig. 117, A, It). The members of each whorl 

 are connate at the base : from this narrow collar each sporophyll 



<^ <3 t^^ O, 



Fig. 117. A, B. Cheirostrohus pettycurensis Scott. (After Scott.) 

 C, D. Pseudobornia ursina Nath. (After Nathorst.) 

 Diagrammatic radial longitudinal section of part of the cone-axis and two 

 sporophylls. It, bundle passing out to sporophyll ; /, fertile segment of 

 sporophyll showing two sporangia; s, sterile (lower) segment. 

 B. Part of transverse section, x, stele ; It, It', bundles on their way to 

 sporophylls ; a, tips of sterile segments of lower sporophylls. 

 Palmately branched leaf (h natural size). 

 Node of stem showing leaf-bases. 



A. 



C. 

 D. 



branches into an upper or dorsal and a lower or ventral limb 

 (fig. 117, A,/ and s). Each limb divides palmately at a short 

 distance from its origin into three slender segments, which 

 extend in a horizontal direction and terminate in large laminar 

 expansions (fig. 117, B, s) to afford a protective covering to the 

 surface of the cone. The upper set of three segments, consti- 



