PERIODS OF FLOWERING. 233 



starch, lose it when the plants shoot out a flowering stem. This is 

 seen in the case of Carrots and Turnips, in which the succulent roots 

 become fibrous and unfit for food when the plants are allowed to run 

 to seed. The receptacle of the Artichoke, and many Compositse, which 

 is succulent before the expansion of the flowers, becomes dry as the 

 process of flowering proceeds. The juices of plants then, when re- 

 quired for the purpose either of food or medicine, ought in general to 

 be collected immediately before flowering. 



479. By cutting a ring out of the bark of trees, and thus retarding 

 the descent of the sap, the period of flowering is sometimes hastened. 

 Again, when the period of flowering is long delayed, either naturally, 

 as in Agave and several palms, or artificially, the process, when it does 

 begin, proceeds with amazing rapidity and vigour. In such cases this 

 vigorous flowering is often followed by the death of the plant. Richard 

 mentions, that a plant of Agave, which had not flowered for nearly a 

 century, sent out a flowering stem of 22^ feet in 87 days, increasing at 

 one period at the rate of one foot a day. Common fruit trees, when 

 they begin to flower, often do so luxuriantly ; but if, from the season 

 being bad, there is a deficiency in flowering, it frequently happens that, 

 from the accumulation of sap, the next year's produce is abundant. 



480. If plants are allowed to send out their roots very extensively 

 in highly nutritive soil, the tendency is to produce branches and leaves 

 rather than flowers. In such cases, cutting the roots or pruning the 

 young twigs may act beneficially in checking the vegetative functions. 

 In pruning, the young shoot is removed, and the buds connected with 

 the branch of the previous year are left, which thus receive accumu- 

 lated nourishment. Grafting, by giving an increase of assimilated 

 matter to the scion or graft (see section on Fruiting), and at the same 

 time checking luxuriant brandling, contributes to the hastening of the 

 flowering. 



481. The period of flowering of the same plant varies at different 

 seasons, and in different countries. During the winter in temperate 

 climates, and during the dry season in the tropics, the vegetative pro- 

 cess is checked, more especially by the diminished supply of moisture, 

 and the arrestment of the circulation of the sap. The assimilated 

 matter remains in a state of repose, ready to be applied to the purposes 

 of the plant when the moisture and heat again stimulate the vegetable 

 functions. This stimulation occurs at different periods of the year, 

 according to the nature of the climate. By observing the mode of 

 flowering of the same species of plant in successive years, conclusions 

 may be drawn as to the nature of the seasons in a country; and by 

 contrasting these periods in different countries, comparisons may be 

 instituted as to the nature of their climate. Thus valuable floral 

 calendars may be constructed. 



482. Plants are accommodated to the climate in which they grow, 



