DUEATION OF THE LIF^ OF PLANTS. 359 



Compositse, Convolviilaceaa, Plantaginaoese 

 Polygonaoese ...... 



Campanulaoeffi, Leguminosse, Valerianacese 

 Gramineae, Labiatse, Solanaceffi 

 Eosaceae ..... 



Eanimciilacese .... 



Antirrhinums, Onagi'acese . 

 TJmbelliferEe . . . , , . 



12 days. 



13 „ 

 H „ 

 15 „ 

 17 „ 

 20 „ 



22 „ 



23 „ 



Temperature has a great effect in accelerating germination. Thus, 

 Erigeron caucasicum, at a temperature varying from 49° to 53°, ger- 

 minated in ten days ; at a temperature from 66° to 72°, in two days ; 

 Dolichos abyssinicus, at the former temperature, in ten days, at the latter, 

 in three ; Zinnia coccinea, in twenty-two and five days respectively. 



Dtjeation of the Life of Plants. — Plants, according to the 

 duration of their existence, have been divided into annual, biennial, 

 and perennial. 'The firsts of these terms imports that the seed ger- 

 minates, and that the plant produces leaves aad flowers, ripens its 

 seed, and perishes within the year ; the second, that a plant ger- 

 minates and produces leaves the first year, but does not produce a 

 flowering stem, nor ripen its seed, till the second, after which it 

 perishes ; while the third intimates that the process of flowering and 

 fruiting may be postponed till the third year, or any indefinite period. 

 The first two exercise the function of flowering in general only once, 

 whUe the last may do so several times before dying. Under different 

 climates, however, and under different modes of management, the 

 same species may be annual, biennial, or even perennial. Thus,. 

 Wheat in this country is annual if sown early in spring, but biennial 

 if sown in autumn ; in hot climates Lolium perenne proves annual ; 

 the Castor-oil plant in 'this country is annual, while in Italy it is a 

 shrub of several years' duration ; the annual Mignonettej by removing 

 its flower-buds the first year, and keeping it in a proper temperature 

 during the winter, may be rendered perennial and shrubby. Many 

 flowering garden plants, as Neapolitan Violet and Lily of the Valley, 

 may be brought into flower at a late period of the year, by pinching, 

 off the blossoms in the early part of the season. 



Plants, as regards their flowering and fruiting, have also been 

 •divided into monocarpic {/iovoe, one, and •/.a.^'itoi, fruit), or those which 

 flower once only and then die ; and polycarpic ('TroXiig, many), or those 

 which flower and fruit several times before the entire plant dies. 

 Thus, annuals and biennials, which flower the first or second year 

 and die, as well as the Agave, and some Palms which flower only once 

 in forty or fifty years, and perish, are monocarpic ; while perennials 

 are polycarpic. Some perennial woody plants live to a great age. 

 The Baobab of Senegal, the WeUingtonia, the Dragon-tree, the Yew, 

 the Oak, the Lime, the Cypress, the Eucalyptus, the Olive, the Orange, 

 Banyan, and Chestnut, often attain great longevity. 



