68 SELBY: STUDIES IN ETIOLATION 
portions of the normal stems. At the end of the period of growth 
studied, four weeks later, the thick cotyledons of the normal 
specimens were very much shrunken, discolored and decaying, 
while those of the etiolated plants were bright, plump, and yet 
retained reserve material. The contrast in this depletion of stored 
food was quite clear. An examination of the roots was made at 
the end of fourteen weeks and the total length of the roots of the 
etiolated plants was found to be about half that of the normal. 
The crowded and entangled growth of the roots of the normal 
plant was in marked contrast to that of the etiolated. A number 
of buds on the basal portion of the etiolated stems, including those 
axillary to the cotyledons, started into activity, but those of the 
normal stem remained dormant. 
The cross-section of the middle portion of the normal stem 
(plate 4, figure 1) showed a fairly well developed woody cylinder 
about 300 » thick, with definite cambium and numerous vessels in 
the wood. The bast-bundles were 48 in number, composed of 
lignified cells with laminae 3.5—4 thick, interspersed at times 
with unlignified, thin-walled cells; occasionally these latter con- 
tained chloroplasts. Usually the secondary bast-bundles were 
fairly well developed. The remaining cortex consisted throughout 
of thin-walled cells with a layer of more highly colored cells just 
without the bast, the whole covered by the unmodified epidermal 
cells. The cells of the pith frequently contained starch and the 
perimedullary ring was gorged with starch, as were also the 
medullary rays. The region of highly colored chloroplasts con- 
stituted also a well-marked starch ring at the base of the normal 
stem. 
The cross-section of the etiolated stem (plate 4, figure 2) 
showed a woody cylinder 150-250 thick, consisting of slightly 
lignified cells, with less conspicuous cambium and with fewer and 
slightly smaller vessels in the wood. The bast consisted of the 
same number of bundles but with very slight development of the 
secondary bundles ; the walls were thinner than in the normal and 
less lignified. The cortex contained fewer chloroplasts than the 
normal, while the two outer layers of the epidermal system were 
more or less collapsed and were underlaid by a well-marked 
hypodermal phellogen. The pith-cells of the etiolated stem were 
