the Sporophylls of the Cycadaceae. 235 
considerable and constant quantity of centripetal 
xylem, with small inverted strands on their dorsal 
side, structure exactly resembling that of bundles in 
peduncle of Stangeria ; large strand supplying mega- 
sporangium has almost completely concentric structure 
with few primary tracheides in central pith. 
Stangeria, d : two bundles in stalk with purely endarch 
structure. 
: — $ : two to four bundles in stalk, of which two 
lateral ones supplying sporangia are much larger in 
size ; centripetal xylem of two or three tracheides 
only in one Or two bundles. 
Bowenia, d : number of very small bundles in stalk, irregu- 
larly orientated, and with purely endarch structure. 
? : four principal bundles in stalk, of which two 
lateral are largest ; few tracheides of centripetal xylem 
always present in latter and may also occur in smaller 
bundles ; besides these, occur small bundles on ventral 
side very differently orientated in different sporophylls, 
and sometimes quite concentric in structure. 
Dioon, d : number of small bundles in stalk ; most have three 
or four or more centripetal tracheides. 
? : one of the largest in order, but megasporangia 
relatively small in size ; number of bundles in stalk, 
but extreme base not represented. Lateral bundles of 
row more strongly developed than rest only when 
sporangia they supply are not abortive ; small quantity 
of centripetal xylem present in some bundles. 
Eneephalartos, d • r °w of bundles in stalk, of which some 
are larger than others, and have small amount of 
centripetal xylem. 
$ : one of the largest in order ; bundles in 
stalk resembling those of $ of Cycas in structure, but 
very irregularly orientated and grouped, and more 
curved in shape, some having almost concentric 
