Notes on the Anatomy of Stangeria paradoxa. 29 
persists we have the development of a cambium in relation to which 
the centrifugal xylem is formed, not as a dying-out vestigial structure, 
but with all the appearance of a definite functional tissue. 
Further indication of the connection between these Cycad 
bundles and those of the Lyginopteris type is found in the parallel 
between the comparative histological characters of the centrifugal 
and centripetal tracheids. 
Summary of Results. 
1. Stangeria possesses a stem with a feebly developed single 
ring of xylem, the groups of which are widely separated from one 
another. 
2. The tracheids are, except for the protoxylem, thickened in 
a rather loose scalariform manner. Pitted tracheids are not found. 
3. The vascular supply to each leaf generally consists of a 
typical girdle, plus four additional strands running directly from the 
central cylinder to the leaf-base. 
4. The foliar bundles contain both centripetal xylem and 
centrifugal xylem, the two systems being separated in space. The 
latter is formed in radial rows in connection with a cambium and is 
probably all secondary. At the base of the petiole primary centri¬ 
fugal wood connects centripetal and centrifugal secondary. 
5. The centrifugal xylem is a flourishing tissue and not merely 
vestigial. 
6 . From the anatomy of the leaf-base and the characters of 
the pitting of the two kinds of wood it is concluded that there is 
close relationship between the foliar bundles of Cycads and the 
mesarch bundles of Cycadofilicales of the Lyginopteris type. 
Finally I must express my thanks to Professor Seward, who 
has not only suggested the research and obtained the material for 
me, but has also given valuable help and advice at all stages of the 
investigation; to Mr. H. A. Hyde, who assisted me in preparing the 
stem for the examination of the girdle-system, and who took the 
photographs illustrating this article; and to M. M. J. Le Goc for 
the loan of the manuscript of his yet unpublished work, 1 which has 
done so much to clear up many doubtful points in Cycad anatomy. 
1 Published while the present paper was being printed (Annals of Botany, 
Vol. 28, 1914, pp. 183-193). 
Botany School, 
Cambridge. 
November 1913. 
