298 GROWTH 



periods may often be curtailed, and the plant brought into trophic 

 conditions will start into activity in a healthy manner. In some 

 cases it is necessary to intensify the principal features of the rest- 

 ing condition in order to secure growth at an earlier time than 

 that of the end of the natural period. This fact is taken advantage 

 of by gardeners in the process of forcing bulbous and tuberous 

 species in early spring, and in consequence of this principle it is 

 only the early blooming species which lend themselves readily to 

 this training. 



Many species, such as the lichens and mosses, find their optimum 

 of trophic conditions during the winter, and are inactive during the 

 summer, and each season is the time of activity of certain forms 

 adapted to the conditions offered. It is not known whether such 

 plants as the mosses would relinquish their resting period if 

 brought into uniform low temperatures and moisture, or not. 



376. Forcing'. The exposure of seeds and bulbs, tubers and 

 rootstocks to periods of a few weeks of low temperatures and 

 then their cultivation in proper temperatures may result in a de- 

 velopment as much as a hundred days earlier than might be at- 

 tained under natural conditions. As a result of recent investi- 

 gations it is found that subjecting the resting plants to the action 

 of an anaesthetic may reduce still further the duration of the 

 resting period, although such treatment, and indeed nearly all 

 forcing exerts an ultimate depressing or exhausting effect upon 

 the plant. 1 



377. Influence of Temperatures Upon Resting Period. Secure 

 a lot of plants embracing seeds of oaks, hickories, herbaceous 

 perennials and bulbs, and tubers of such plants as Arisaema, Tril- 

 lium, Convolvulus and divide into two portions. Place one in a 

 greenhouse room at 20 to 25 ° C. and the other in a refrigerator 

 at about 8-1 o° C. This should be done at the end of October. 

 Ten weeks later set all the material in moist soil, under proper 



1 Johannsen, W. The forcing of plants by ether. Translation in American Gar- 

 dening. 21 : 358. -1900. 



Bailey, L. H. Cyclopedia of Amer. Horticulture. 2 : 595. 1900. 



