976 Carter.—A Reconsideration of the 
£ Leitungsbahnen ’} Haberlandt 2 describes it, while Worsdell 8 and Miss 
Chick 4 are now to be referred to. 
A paper entitled ‘ On the Origin of “Transfusion Tissue ” in the Leaves 
of Gymnospermous Plants ’ was read before the Linnean Society in March, 
1897. In it the author, Worsdell, suggested that transfusion tissue took its 
origin in £ the successive unlimited centripetal development of the tracheides ’ 
of the centripetal xylem found in the cotyledonary bundles of Cycas and 
Ginkgo. This view was mainly founded on the facts— 
1. That in the cotyledons of Ginkgo biloba and of Cycas revoluta 
a good deal of centripetal wood was found, and that this gradually shaded 
off into typical transfusion tissue. 
2. That centripetal xylem as well as transfusion tissue is present in the 
leaves of certain Conifers, i. e. Cephalotaxus and Taxus as well as in Dam- 
mar a , Araucaria , Widdringtonia, and Pinus. 
Centripetal wood is no longer regarded as a rare phenomenon in the 
leaves and cotyledons of Gymnosperms. 
A paper of much interest in this connexion is that of Miss Chick, 5 who 
found in Torreya that at the base of the cotyledon the protoxylem was 
central; the more internal elements were crushed and could be traced down 
to the metaxylem, while other elements which were not crushed were in 
contact with the primary and secondary xylem of the bundle. At this 
level centripetal xylem elements were found only very occasionally, and 
there were very rare transfusion elements on the flanks of the bundle. 
Both increased upwards, but the centripetal xyjem was greatest in the 
middle and the transfusion tissue at the tip. The writer went on to say 
that it appeared as though the transfusion tissue were being formed from 
the parenchyma outside the bundle, but emphasized the transition in size 
and other characters between it and the xylem. Bernard, 6 though he dis¬ 
agrees with Worsdell with regard to the petiole of Ginkgo , agrees with him 
in the general view that transfusion tissue represents centripetal wood. 
So far as is known to the writer, no one but Worsdell has investi¬ 
gated the cotyledons of Gymnosperms exclusively with regard to the 
origin of transfusion tissue; and it was suggested by Mr. T. G. Hill that 
such an investigation would be profitable ; in addition to this suggestion 
Mr. Hill supplied the material and has been most generous with his help 
throughout. The seedlings used were mostly grown at the Chelsea Physic 
Garden through the kindness of Mr. Hales. Hand sections (transverse and 
longitudinal) of the cotyledons were made and stained with gentian violet 
and vesuvian brown ; others were treated with phloroglucin and others 
1 P. 100 et seq. 2 Physiologische Anatomie, p. 332. 
3 See reference in text. 
4 The Seedling of Torreya Myristica. New Phytologist, vol. ii, 1903. 
6 Loc. cit. 6 Le bois centripete dans les feuilles des Coniferes. 
