316 BOTANICAL GAZETTE | NOVEMBER 
The elliptical endoderm or bundle sheath, which lines the 
mesophyll on its inner side, separating it from the central peri- 
cycle and fibrovascular bundle, consists of one very distinct 
layer of large, usually oval, non-lignified parenchyma cells. 
The pericycle consists of more or less thickened, lignified 
parenchyma cells, destitute of chlorophyll. The greater part of 
it lies on the dorsal side of the leaf, while the vascular bundle 
occupies the ventral. The pericycle consists of two kinds of 
cells, forming two distinct areas. First, a central, well marked 
area with non-pitted cells, varying greatly in size and in the 
thickness of their cell walls (fig. 2). These cells separate with 
2 or 3 layers the two divisions of the vascular bundle in the middle 
part of the leaf, where the bundle is bifurcated. They extend 
up into the ventral or xylem side of the bundle, forming a wedge 
shaped area of thick walled cells. On the phloem side they are 
thinner walled, but larger, and fill up the whole center of the 
pericycle, extending dorsally to the endodermis in the leaves of 
the lateral branches. But in the leaves of the terminal shoots, 
the non-pitted area is separated from the endodermis by a layer 
of the pitted parenchyma. Second, the pitted parenchyma of 
the pericycle, which forms the so-called transfusion tissue of von 
Mohl. This part consists of linear lignified cells with bordered 
pits on their ends, as well as on their lateral walls (fig. 3)- The 
transfusion tissue is not as well developed in the leaves of the 
lateral branches as in the leaves of the terminal shoots. In the 
former there are two small areas, each one lying dorsal to the 
outer half of the two phloem areas. Each area of the transfu- 
sion tissue extends along the endoderm about one-eighth of its 
circumference. In the leaves of the terminal shoots the two 
parts of the transfusion tissue begin at the outer edges of each 
of the phloem parts and follow the endodermis until they meet, 
thus making a semicircular area of transfusion tissue, 2 to 6 cells — 
deep on the dorsal side of the leaf beneath the endodermis.— oF me 
More than one-half of the pericycle of the leaves of the or 
a 
nal shoots consists of transfusion tissues. S . 
The vascular bundle lies near to the endoderm on the poe eeu 
