1040 Chambers.—The Vestigial Axillary Strands of 
Morphology of the Axillary Branch. 
It was found to be difficult to follow the axillary strand into the petiole 
in sections of the whole stem, so petiole bases were separated from the stem 
and examined. Examination with a lens showed, at the base of the petiole 
on the adaxial surface, a small tapering mass of tissue covered with brown 
hairs (Text-fig. 1, b). This tissue came off as a whole in hand sections, so 
the petiole bases were embedded and cut with the microtome. 
In several cases it was found that the division into axillary branch and 
leaf-trace had already taken place, in the cortex of the stem probably, so 
that the two were some distance apart. Other cases showed the meristele 
still undivided, and exhibiting the same characters as when it first came off 
from the stem. The meristele becomes somewhat oval in shape and soon 
shows a band of parenchyma separating off the xylem of one rounded end 
Text-fig. 3 a. Diagram showing the break ( br .) in Text-fig. 3 b. Enlargement 
the cortex separating off the axillary strand ( x ). of a-b from 3 A. 
/, leaf-trace. 
to form the axillary strand (PI. LXXX, Fig. 2). This separation goes on 
gradually until the axillary strand consists of a mass of xylem with 
parenchyma surrounded by phloem, pericycle, and endodermis. In every 
respect this strand resembles in structure the stem stele. 
The leaf-trace has its xylem arranged round two groups of parenchyma 
with the thinner portion of the xylem on the flattened adaxial surface. Two 
groups of protoxylem can be distinguished in the parenchyma (PI. LXXX, 
Fig. 3). Gradually the parenchyma aggregates into one group, and the thin 
band of xylem is interrupted by parenchyma cells, so that the metaxylem 
takes the arched form characteristic of the leaf-trace in Trichomanes . The 
protoxylem is in two groups, one at each incurved arm of the metaxylem. 
The axillary branch strand passes very gradually through the cortex 
and diminishes in size. PI. LXXX, Fig. 4, gives its structure when it is 
0-075 mm - away from the leaf-trace. As it moves further away the amount 
