Takeda. — A Theory of ‘ Transfusion- tissue'. 361 
and smaller bundles which form a dense network, and can conduct and supply 
water to every part of the leaf, and it is not similar to the case of certain 
Cycads or broad-leaved Podocarps. Another objection is that the cells are 
so short that there must be much disadvantage in conducting water. Lastly, 
the tissue is better developed near the apex of the leaf, where conduction of 
water is less necessary. 
If we look at this tissue without such prejudice there seems to be no 
reason why we could not regard it as a water-storage organ. I may 
perhaps give here some examples of similar tissue occurring in the Angio- 
sperms. It is very familiar to us that the termination of vascular bundles 
in the leaves of various Dicotyledons is provided with short water-storing 
tracheides. In some cases, as shown by Heinricher ( 5 ) in Capparis 
spp., Centaurea spp., and Astrolopium repandum , and as in Armeria 
vulgaris , the water-storing tracheides extend much further down, and 
frequently occur even for some distance along vascular bundles. These 
strongly remind us of the ‘ transfusion- tissue ’ in the leaf of Gnetum 
( 9 , p. 626 ; 12 , p. 149) and in the cotyledon of Welwilschia ( 13 ). To give 
another example, it is well known that epiphytic Orchids have adapted 
various organs for water storage. In spite of the tremendous amount of 
aqueous tissue of parenchymatous cells, the stem of certain species of 
Dendrobium possesses thick-walled tracheide-like water-storing cells along 
the bundle, which are arranged in the same fashion as we see in the 
adult leaf of Welwilschia. Of course, broad-leaved plants store water 
in a rather different way from what is seen in the Gymnosperms, namely, 
in most cases by parenchymatous aqueous cells. Still, if we examine 
those Angiosperms 1 which possess only scaly or acicular leaves, the water- 
storing device is just as we see it in the Gymnosperms. An interesting 
case of occurrence of water-storing tracheides in the pith 2 of Cephalo- 
taxus Koraiana has been recorded by Rothert (8). These tracheides are 
more or less isodiametric in shape, resembling the ‘ transfusion-tracheides ’ 
in the leaf, and have reticulated bars and bordered pits. It is worthy of 
special notice that these tracheides are, according to the author, derived 
from parenchyma and do not indicate any sign of vestigial centripetal xylem. 
Scheit ( 9 , p. 632) has pointed out that ‘ transfusion-tissue ’ is much more 
abundant in the leaves of those Conifers which grow in dry localities than 
those growing in damper places (this point is reversely referred to in 
Miss Carter’s paper, p. 982). This fully shows that this tissue is nothing but 
a water-reservoir brought forth by physiological necessity. If it is not, 
where could we find water-storing tissue in the Gymnosperms ? 3 
1 E.g. Casuarinarae ; many species of Tamaricaceae ; certain members of Proteaceae, such as 
Persoonia, Franklandia, &c. 
2 Comparable with the parenchymatous water-storing cells in the pith of Ledum palustre. 
3 In the cladode of Phyllocladus isolated parenchymatous water-storing cells are present. This 
is probably unique among the Gymnosperms. 
