A Theory of * Transfusion-tissue 
BY 
H. TAKEDA. 
T HE ‘transfusion-tissue’, first described by Frank (4, p. 167, Taf. iv), 
afterwards named and more emphasized by von Mohl (7, p. 10), and 
more recently thoroughly investigated by Worsdell (14), has been stated 
by the last-named author to ‘ have been phylogenetically derived from the 
centripetally formed xylem of the vascular bundle ’ and to serve ‘ as an 
auxiliary conducting-system’ (14, p. 318), a view which has been more 
fully elaborated by Bernard (1), and seems to be universally accepted by 
modern eminent botanists. 
In an interesting paper recently published, Miss Carter (3) shows that 
in the cotyledon of certain Conifers examined by her, the first-formed 
elements of this tissue always arise on the lateral side of the bundle, but 
not, even where centripetal xylem is present, on the adaxial side of the 
bundle. This fact well corresponds to the case which I have described 
in the cotyledon of W elwitschia mirabilis (13, p. 354)- It is well known 
that the vascular bundles in the adult leaf of this plant are completely 
surrounded by a sheath of ‘ transfusion-tracheides ’. Development of these 
tracheides takes place at the lateral side of the vascular bundle, as it does 
in the case of the cotyledon, and later scattered elements appear on the 
xylem side or the phloem side, or both, without any intimate connexion, 
and afterwards a complete sheath of one or occasionally two layers of 
tracheides is formed (13). These ‘ transfusion-tracheides’ are, in the main, 
parallel bundles, always separated by masses of unlignified sclerenchymatous 
fibres on the upper and lower sides of the bundle, for these fibres become 
differentiated very early, prior to the formation of the ‘transfusion-tracheides’, 
so that connexion between the xylem and ‘ transfusion-tissue ’, if at all, 
is only to be established on the lateral side of the vascular bundle. 
The lateral origin of ‘ transfusion-tissue ’ was already described by 
Scheit (9, p. 6% 8) thirty years ago in the adult leaves of the Conifers. It 
always starts on the lateral side of the vascular bundle and in the pericyclic 
region of that. 1 The tissue extends in general horizontally and forms wings, 
1 Scheit (1. c.) has attributed the elongated form of the first-made elements to the influence of 
stretching of the xylem. This is, however, probably due to the fact that these elements arise in the 
pericycle. 
[Annals of Botany, Vol. XXVII. No. CVI. April, 1913.] 
