120 MR. W. C. WORSDELL ON TRANSFUSION-TISSUE 
in the bundles of the leaves of Cycads. Moreover, these 
tracheides were very much scattered. In proportiou as they 
receded further from the protoxylem towards either side of the 
bundle, they attained a greater diameter and, what more 
especially distinguished them, they were provided with reticulate 
thickenings on their broad transverse walls. In fact, they 
presented very mueh the appearance of the tracheides composing 
Ry 
Transverse section of vascular bundle from the upper part of the cotyledon of 
Gingko oiloba. ph=pbloem ; pz=protoxylem ; x!=centripetal xylem; 
x* =transfusion-tissue, 
the transfusion-tissue in the leaves of Coniferæ. One or two of 
these tracheides which most completely resembled transfusion- 
tissue were situated quite on the side of the bundle and bordering 
on the phloem. In longitudinal section a most evident transition 
was seen between those tracheides nearest the protoxylem, which 
are elongated and narrow in shape, and those farthest removed 
from the latter, which are short and broad and in every way 
similar to the elements of the transfusion-tissue in Coniferous 
leaves. 
In the bundles of the petiole of the foliage-leaf of Gingko 
there is a great development of the secondary centrifugal wood. 
Bat here also, on the inner or ventral side of the protoxylem, 
were seen two or three small tracheides of centripetal xy lem. 
On the side of the bundle at the level of the phloem a few 
elements of typical transfusion-tissue were observed. 
A study of the structure of the bundles in the cotyledons of 
Cycas revoluta revealed something very similar to the above 
Here, as in Gingko, there was a relatively small development 
