IIo EVANS—EFFECT OF ENVIRONMENT ON THE 
PART “li. 
The description of the minute anatomy of seedlings of Luzula 
given by Laurent (1), in his excellent and exhaustive treatise on 
the development of the Juncacez, is that of surface germinated 
plants. He shows the hypocotyl as extremely short, and speaks 
of the almost immediate change from root arrangement (alter- 
nating) to cotyledonary arrangement (superposed) of the xylem 
and phloem in the vascular system. I was anxious to ascertain the 
structure found in the elongated hypocotyl, in case the transition 
should prove more gradual; and J also determined to examine 
seedlings at a later stage than those observed by Laurent, so that 
they might have had time to develop sufficiently to give some 
idea of the passage from hypocotylar to shoot arrangement. Un- 
fortunately the results of this quest—which proved much more 
difficult than I expected—were very unsatisfactory. Sections 
were cut both by hand and in the microtome, the specimens being 
embedded in paraffin in the latter case, using xylol as the solvent 
for the wax. The comparatively large size of the thin walled, 
almost empty cortical cells made it impossible to prevent them 
from being crushed during the process of infiltration ; while hand 
cut sections were not sufficiently fine for the purpose, and the 
tissues had not enough strength to resist the razor well when un- 
embedded. Other difficulties were the numerous lateral roots 
which disturbed the vascular arrangement at short intervals ; and 
the very imperfect differentiation of xylem and phloem due partly 
to the youth of the seedlings, partly to the transitory nature of 
the hypocotyl. First, then, I shall describe a transverse section 
through the hypocotyl, cut about midway between its extremities ; 
and shall afterwards explain, as far as I have been able to make 
them out, the changes which take place on passing downwards or 
upwards from this point. 
In such a central section we find a vascular core, completely 
surrounded by a very well marked endodermis, and representing 
about one-third of the diameter of the hypocotyl. The tissues to 
the exterior of the endodermis, forming the cortex, are composed 
of large, thin-walled cells, almost devoid of contents, thus giving 
a very transparent appearance to the axis when examined as a 
whole. The cells of the outermost layer of this cortex do not 
