450 MR. W. C. WORSDELL ON THE 
related to Cycads, I may recall the primary concentric bundles 
in the petiole of Lyginodendron*, and in that of Calamopitys 
Satwrni of Ungert. In another nearly allied fossil group, 
however, the Medullosee, the petioles, generally known under the 
name of Myeloxylon, usually possess collateral bundles; but 
the small concentric strands occurring in abundance in the cortex 
of some specimens of stems of Medullosa are leaf-traces t, 
although before entering the leaves they split up into collateral 
bundles. Regarding, then, these concentric bundles in Stangeria 
as primitive structures, it is but natural to find the region where 
the bundles are most clearly concentrie to be the upper part of 
the cotyledonary stalk, which is, in all probability, the oldest part 
of the organ, so that the bundles from this point run through 
tissues which, in the upper part of the organ, have been 
formed by later apical, in the lower part by later intercalary 
growth. 
The young foliage-leaf which the seedling bore possesses à 
lamina consisting of four leaflets (Pl. 20. fig. 12). The bundles of 
the petiole, in its lower part, are three in number, corresponding to 
the blunt, triangular form of the organ. Each bundle has a few 
large, centripetal tracheides, and often, but not always, one or two 
small centrifugal ones. 
About two-thirds of the way up the petiole are one or two 
small sharp projections, like remnants of spines. These show 
periderm formation on their inner side, offering the appearance 
in section as if some appendage had been there cut off : they may 
possibly represent rudiments of pinne §. In the uppermost part 
of the petiole just below the lamina the bundles are four in 
number, one or two of which, by their double protoxylem, show 
signs of forking. The petiole has here two lobes on the ventral 
face. 
The midrib of the pinna has two bundles, each with one or 
two centrifugal tracheides. The bundles in the mesophyll are 
exceedingly small, often containing only two or three small 
* Williamson & Scott: “ Further Observations on the eni Plants of the 
Coal Measures," iii i . al Soc. 1896. 
t Solme-Laubach eese doe Untereilm von Saalfeld," Abhandl. d. 
k. Preuss. Geol. Landesanstalt, neue Folge, Heft 23, p. 65, plate iv. (1896). " 
1 Weber & Sterzel : ‘ Beiträge zur Kenntniss der Medulloseæ, pP- 17-49, 
figs. 7 & 8 in text, fig. 2, plate i., figs. 1-4, plate iii. (1896). 
Solms-Laubach : * Ueber Medullosa Leuckharti,” Bot. Zeit. 1897. 
§ F. O. Bower, in Phil. Trans. vol. 175. p. 590. 
