EFFECT OF LIGHT ON PLANTS GARNER AND ALLARD. 583 



days of winter so far as concerns effect on flowering and fruiting. 

 This does not mean, however, that artificial light of low intensity 

 may be used to replace entirely the sunlight, for in this case most 

 if not all of the plants would fail to develop normally and, in fact, 

 many would soon perish. 



CAUSE OF EVERBLOOMING AND EVERBEARING. 



Numerous examples have been cited in preceding paragraphs 

 which illustrate the fact that a certain day-length will cause prompt 

 flowering and fruiting, the particular day-length required varying 

 widely with the species. On the other hand, certain day-lengths may 

 inhibit or greatly delay flowering and fruiting while greatly favoring 

 vegetative development. Under these latter conditions the plant 

 may continue to grow almost indefinitely without flowering, thus 

 attaining abnormally large size. Profuse flowering and fruiting of 

 plants usually arrests growth either temporarily or permanently, so 

 that profuse flowering and rapid vegetative devolopment are more 

 or less incompatible. Seeing that in a given species a certain day- 

 length may be conducive only to vegetative development while an- 

 other day-length may favor only the flowering and fruiting phases 

 of development, the question arises as to the behavior of the plant 

 when exposed to an intermediate length of day. As a matter of 

 fact, the intermediate day-length tends to favor both phases of plant 

 development, and this situation whereby the plant divides its energies 

 between growth on the one hand and flowering and fruiting on the 

 other hand in reality constitutes the " everblooming " or " ever- 

 bearing" condition. Instead of a short period of profuse flowering 

 and fruiting, with resultant cessation of growth, there is a more or 

 less extended period of relatively sparse flowering and fruiting, the 

 plant all the while continuing to grow more or less. Naturally, 

 there may be all gradations between the purely vegetative and the 

 flowering and fruiting conditions, depending on the relative degree 

 to which the prevailing length of day may favor these two alterna- 

 tive phases of plant activity. It follows that in a given latitude the 

 duration and the rate of flowering and fruiting of a given species is 

 likely to be controlled in large measure by the season of the year at 

 which the plant is grown, and likewise the behavior in one latitude is 

 likely to differ from that in another latitude because of difference in 

 the prevailing length of day. For example, buckwheat (Fagopyrum 

 ■vidgare Hill) sowed November 1 in the greenhouse under normal 

 conditions began to flower during the first week in December and by 

 February had ceased flowering and soon afterward died, having 

 reached a height of about 21 inches. A similar planting in the 

 greenhouse in which electric light was used for a part of the night 



