﻿284 BOTANICAL GAZETTE [april 



were removed from the pieces in one lot; both lots were then placed 

 on wet soil in pots and covered with excelsior, which was kept con- 

 stantly wet. Within 10 days all the stem pieces with skins removed 

 bore sprouts from eyes near the cut surface. The stem pieces with 

 skins on began to sprout on the 20th day. Figs. 1 and 2 show the 

 growth of sprouts on the 24th day. It will be seen from this experi- 

 ment that even with the skin intact the buds near a cut surface 

 begin to sprout much earlier than normally, provided the exposed 

 surface is kept moist and suberization thereby retarded. The buds 

 on the pieces with skins removed not only sprouted still earlier, but 

 the sprouts also grew much faster. 



On November 13, tubers harvested on November 4 were cut in 

 half transversely to the long axis. The stem halves were then divided 

 into two lots of 5 each. The cut surfaces of one lot were immedi- 

 ately dipped into warm paraffin. When the paraffin cooled, form- 

 ing a thin layer over the surface, both lots were placed in paper sacks 

 and stored in a dark, dry laboratory closet. On December 18 all of 

 the paraffined halves bore sprouts from buds near the cut surface. 

 The surface underneath the paraffin was still moist and the cell 

 walls very little suberized. The paraffin in drying cracked from 

 the edges sufficiently to allow free access of air. The cut surfaces 

 of those not dipped in paraffin were dry and heavily corked; these 

 did not begin to sprout until a month later. It seems very 

 probable that the surfaces kept moist by paraffin and not al- 

 lowed to suberize admitted something to the near-by buds which 

 was not so freely admitted through the heavily corked surfaces. 

 It could not be water, as the sprouting occurred in a dry atmosphere. 

 The other alternative is oxygen. The earlier sprouting in the case 

 of the paraffined pieces was not the result of heat applied to the cut 

 surface by the warm paraffin ; this was proved when the experiment 

 was repeated, using a third lot which was dipped in paraffin, the 

 paraffin being removed as soon as cold. This lot sprouted no earlier 

 than the one not treated. 



Effect of light.— Planting tubers with the stem ends in soil 

 and covering the seed ends with wet excelsior exposes the latter to 

 subdued light; it is sufficient, however, to induce rather rapid green- 

 ing of the exposed part of the tuber. It soon became evident by 



