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 i) showed a fairly well developed woody cylinder 

 about 300 (i 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 

 showed a woody cylinder 150-2 50 fi 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 



