214 FLOWERING AND ITS CONSEQUENCES. 



as 73. During this dry season, when the scorching sun reduces 

 the soil nearly to the dryness and consistence of brick, ordinary 

 vegetation almost completely disappears ; and the Fig-Marigolds, 

 Euphorbias, and other succulent plants, which, fitted to this condi- 

 tion of things, alone remain green, not unaptly represent the Firs 

 and other evergreens of high northern latitudes. The dry heat 

 there brings about the same state of vegetable repose as cold with 

 us. The roots and bulbs then lie dormant beneath the sun-burnt 

 crust, just as they do in our frozen soil. When the rainy season 

 sets in, and the crust is softened by moisture, they are excited into 

 growth under^a diminished temperature, just as with us by heat; 

 and the ready-formed flower-buds are suddenly developed, cloth- 

 ing at once the arid waste with a profusion of blossoms. The 

 vegetation of such regions consists mainly of succulents, which are 

 able to live through the drought and exposure ; of bulbous plants, 

 which run through their course before the drought becomes severe, 

 then lose their foliage, while the bulb remains quiescent, safely 

 protected under ground until the rainy season returns ; and of an- 

 nuals, which make their whole growth in a few weeks, and ripen 

 their seeds, in which state the species securely passes the arid sea- 

 son. A season of interruption to growth, produced either by cold 

 or dryness, occurs, in a more or less marked degree, through every 

 part of the world. 



376. These considerations explain the process of 'forcing plants, 

 and other operations of horticulture, by which we are enabled 

 to obtain in winter the flowers and fruits of summer. The gar- 

 dener accomplishes these results principally by skilful alterations 

 of the natural period of repose. He gives the plant an artifi- 

 cial period of rest by dryness at the season when he cannot com- 

 mand cold, and then, by the influence of heat, light, and moisture, 

 which he can always command, causes it to grow at a season 

 when it would have been quiescent. Thus he retards or advances, 

 at will, the periods of flowering and of rest, or in time completely 

 inverts them. 



