PLATE 8 
A. —Underground portion of Irish potato plant of the McCormick variety. This 
plant was grown in the greenhouse during the summer months and received electric 
illumination from sunset till midnight in addition to the natural daylight. No tubers 
were formed, and while flower buds appeared they were unable to open. Instead of 
becoming tuberized some of the buds borne on die underground stems at once ger¬ 
minated and formed offsets, thus eliminating the usual rest period. The aerial 
stems of the mother plant reached unusual heights. As the length of day was pro¬ 
gressively reduced there was corresponding increase in tuber formation (see text, 
page 891). 
B. —Plants of table beet, roots of which had been stored in an outdoor pit during 
the previous winter. Plants at left were exposed to the full seasonal length of day, 
beginning April 1, and began flowering in June. Plants at right, exposed to a io-hour 
day began the development of flowering stems but were unable to flower, the apex 
of the stem being transformed into a leaf rosette. The branches and leaves are more 
numerous than under the longer day. Photographed June 14. 
