WorsdelL — The Structure mid Origin of the Cycadaceae. 145 
cases I regard these inner bundles as an ancestral remnant of the inner- 
most cylinder of primary bundles above described in certain Medul- 
loseae. The same will hold good for the two primary cylinders in the 
peduncle of the cone in Encephalartos , of which the outermost, divided 
up into irregularly formed groups of concentrically-arranged bundles, 
supplies the sporophyll-traces. Matte gives beautiful illustrations of this 
pleiocylindric character in the peduncle of the cone of Encephalartos villosus 
(Fig. 11). 
The inversely orientated strands occasionally occurring on the dorsal 
side of the bundles of the normal cylinder or arc of the peduncles and 
sporophylls respectively, receive also their explanation from a study of 
Medullosean anatomy. This phenomenon is due to the presence in that 
position of a stele, or 
the rudiments of such, 
which, instead of, as in 
the case of the usual 
bundles of the cylinder 
or arc, lacking the ven- 
tral portion of the pri- 
mitive stele, exhibit a 
complete abortion of 
the dorsal half thereof. 
But in one or two cases, 
signs of slight cambial 
activity on the outer 
side of such strands 
indicate an attempt at 
reversion to the primi- 
tive state of things. 
Frequently these 
strands are continuous 
with those of the nor- 
mal cylinder by means of an involution of their tissues ; this is also the 
same phenomenon as was described by Gregg in the root of Cycas See - 
manni\ in that case, however, the outer half of the usually incomplete 
stele is present, and is continuous as an independent continuous zone right 
round the entire root-stele. 
In the case of the cone the inversely orientated dorsal strands are 
primary ; hence we here see another instance of the presence of two 
primary cylinders (or parts of such) like those already described. As a 
comparison with what I found in the case of Encephalartos , we may 
note that Scott says, speaking of Ceratozamia : c some of these [inverted 
cortical] bundles, where they pass further out into the cortex, show some 
L 
Fig. 11. Encephalartos villosus : transverse section of part of 
vascular system of peduncle of cone, showing outer primary ring 
consisting of groups of bundles (after Matte) (diagrammatic). 
