402 Scott. — On Peduncle of Cycadaceae . 
It is in the male peduncle of S t anger ia that the centripetal 
wood reaches its greatest development, and this case will 
therefore be first described. 
Stangeria paradox a, T. Moore . 
General Structure . The principal vascular bundles of the 
peduncle, varying from 12 to 18 in number, are ranged in 
a single ring, which is fairly regular in the upper and middle 
part of the organ, but becomes much distorted towards its 
base, where the orientation of the bundles also becomes 
irregular (cf. Figs. I and 2). Lower down still, where the 
peduncle is about to pass over into the main stem, of which 
it forms the direct prolongation l , the vascular ring once more 
becomes perfectly regular, but with a much smaller diameter, 
and a reduced number of bundles. Some peculiarities in the 
course of the vascular strands will be further considered below. 
The structure of a normal main bundle is as follows. The 
centrifugal wood in the mature peduncle reaches a radial 
thickness of about 12 elements; the scalariform tracheides 
are closely packed, though the mass is broken up here and 
there by bands of parenchyma, which do not always form 
continuous medullary rays. On the inner side of each bundle 
there are two or more groups of spiral or annular tracheides, 
constituting the protoxylem. These elements soon become 
crushed by the growth of the turgescent parenchyma around 
them (see Figs. 3 and 4, px). The elements of the centrifugal 
wood do not show such regular seriation as in some other 
Cycads, though their number is certainly added to, for 
a long time, by the activity of the cambium. 
The phloem is extremely well developed, and usually 
exceeds the xylem in bulk. Many of the individual sieve- 
tubes are larger than the tracheides, especially in radial 
Mr. W. C. Worsdell, who prepared numerous sections of peduncles, at my 
request. 
1 Solms-Laubach, Die Sprossfolge der Stangeria und der iibrigen Cycadeen : 
Bot. Zeit. 1890. 
