TLOWERING AN EXHAUSTIVE PROCESS. 205 



Annuals flower in a few weeks or months after they spring from the 

 seed, when they have little nourishment stored up in their tissue ; 

 and their lives are destroyed by the process (144) : biennials flower 

 after a longer period, rapidly exhausting the nourishment accumu- 

 lated in the root during the previous season, and then perishing 

 (145) ; while shrubs and trees do not commence flowering until 

 they are sufficiently established to endure it. The exhaustion con- 

 sequent upon flowering, however, is often exhibited in fruit-trees, / 

 which, after producing an excessive crop (especially of late fruits, , 

 such as apples), sometimes fail to bear the succeeding year. Wlien 

 the crop of one year fails, the nourishment which it would have ap- 

 propriated accumulates, and the tree may bear more abundantly the 

 following season, and so on alternately from year to year. 



368. The actual consumption of nourishment in flowering may 

 be shown in a variety of ways ; as by the rapid disajapearance of 

 the farinaceous or saccharine store in the roots of the Carrot, Beet, 

 &c. when they begin to flower, leaving them light, dry, and empty ; 

 and by the rapid diminution of the sugar in the stalks of the Sugar- 

 cane and of Maize at the same period. The stalks are therefore | 

 cut for making sugar just before the flowers expand, when they | 

 contain the greatest amount of saccharine matter. 



369. The consequences of this exhaustion upon the duration of 

 plants are further illustrated by the facility with which annuals may 

 be changed into biennials, or their life prolonged indefinitely by 

 preventing their flowering ; wliile they perish whenever they bear 

 flowers and seed, whether during the first or any succeeding year.. 

 Thus, a common annual Larkspur has given rise to a double-flowered 

 vai'iety in the gardens, which bears no seed, and has therefore be- 

 come a perennial. Cabbage-stumps, which are planted for seed, may 

 be made to bear heads the second year by destroying the flower- 

 shoots as they arise ; and the process may be continued from year to 

 year, thus converting a biennial into a kind of perennial plant. The 

 effect of flowering upon the longevity of the individual is strikingly 

 shown by the Agave, or Century-plant, — so called because it flow- 

 ers in our conservatories only after the lapse of a hundred, or at 

 least a great number of years ; although, in its native sultry climate, 

 it generally flowers when five or six years old. But whenever this 

 occurs, the sweet juice with which it is filled at the time (which by 

 fermentation forms pulque, the inebriating drink of the Mexicans) is 

 consumed at a rate answering to the astonishing rapidity with which 



18 



