118 MR. We C, WORSDELL ON TRANSFUSION-TISSUE 
On the Origin of “ Transfusion-tissue ” inthe Leaves of Gymno- 
spermous Plants. By W. C. Wordbur. (Communicated 
by D. H. Scorr, F.R.S., F.L.S., Hon. Keeper of the Jodrell 
Laboratory, Royal Gardens, Kew.) 
[Read 18th March, 1897.] 
THERE is a species of conducting-tissue occurring in the green 
parts of certain plants which for long has been known by the 
name of transfusion-tissue. It occurs principally in the leaves of 
Gymnosperms, but is not exclusively confined to this group of 
plants. It is found most usually in direct connexion with a 
vascular bundle, and extending out from this among the cells of 
the surrounding parenchyma, and consists of tracheides, short 
and parenchymatous in shape, which are often accompanied by 
bast-cells. It doubtless serves as a secondary conducting-tissue 
for those leaves whose vascular bundles are few or widely 
separated, and are not supplied with a complex system of veins 
such as is found in Dicotyledonous plants. It is most abundantly 
represented in the leaves of Conifers, where it is universal ; it is 
also found in the leaves of nearly all Cycads. In these two 
orders of plants the transfusion-tissue occurs almost always in 
lateral connexion with the vascular bundle. But it is also found 
in a few genera all round the bundle, in others on the outer 
periphery of the phloem, and in others again opposite the xylem. 
As regards the origin of this tissue there are various views: 
some consider that it forms part of the conducting-tissues of the 
vascular bundle to which it is attached; others consider that it 
belongs to the parenchymatous ground-tissue of the leaf ; finally, 
the French botanist, Van Tieghem, maintains that it is part of 
the pericycle surrounding the bundle. While the latter view 
may be perfectly correct as far as the ontogenetic origin of the 
elements composing this tissue is concerned, my own investi- 
gations go to show that, phylogenetically, this tissue has at 
origin agreeing with that assumed by the first of the above views, 
viz. from the vascular bundle it:elf, though in a manner Very 
different from what the authors of this view suspected. 
I will first of all describe the structure of a bundle from 2n 
ordinary foliage-leaf of a Cycad, sc as to pave the way for my 
subsequent remarks. It is well-known that the vascular bundles 
of the leaf of Cycads have a structure peculiar to this order and 
not found in any other living group of plants. Towards the 
