Relation of Pteridosperm Anatomy to that of Cycads, 59 
upon evidence derived from a consideration of vascular structure (a) 
in the cotyledonary node, where, he considers, ancestral traits are 
likely to be found in the earliest vascular tissues; and (b) in the 
flowering axis, for it is held that here the vascular tissue will have 
undergone less modification on account of conduction than is the 
case with the vegetative stem. 
With regard to the first point, Worsdell believes that the coty¬ 
ledonary node of certain Cycads exhibits structural peculiarities 
which indicate, to a great extent, the origin of the vascular structure 
as a whole. Cycas siamensis (7; Fig. 13), Cycas Seemanni (5; 22), 
Fig. 13 .—Cycas siamensis. Transverse section of vascular system of seedling 
axis in region of cotyledonary node, showing outer ring of steles. (Adapted 
from Worsdell, 1906, after Matte). 
Cycas revoluta (20), Encephalartos horrid us (21), Macrozamia Denisonii 
(22), and Bowenia spectabilis (22) show concentric vascular strands 
surrounding the main axis. These give the seedlings an appearance 
of polystelic structure in this region, constituting the first extra- 
fascicular ring. Worsdell believes them to be the remnants of an 
ancestral solenostelic or polystelic structure derived from such a 
form as Medullosa porosa or Medullosa Leuckarti. 
A seedling of Encephalartos Barteri described by Matte (7) 
shows three almost independent steles in place of the usual endarch 
cylinder (Fig. 14). Worsdell, in complete agreement with Matte, 
