DURATION OF VARIETIES OF PLANTS. 



sive to active vitality, but it cannot be said to be a renewal of vitality, any more than the 

 awakening of a dor-mouse, or other hybernating animal, can be said to be a renewal of 

 its vitality. It is the same vitality throughout life, only differing in power as the measure 

 of life progresses, and maintaining its ascendency for a longer or shorted period, according 

 to the original vigor of the constitution, and to the favorable or adverse circumstances to 

 which individuals may have been exposed. The periods of youth, maturity, and old age, 

 are, indeed, sufficiently well marked in fruit and forest trees, and the changes induced by 

 age have been observed and described by Knight, Loudon, and other writers, and ma}'' 

 be briefly summed up. We find a tree in its youth grows with rapidity, exulting as it 

 were, in its vigor and health; as it reaches maturity the exuberance of its growth is check- 

 ed, and its energies are chiefly directed to the production of fruit or seed; as old age ad- 

 vances, the foliage is first seen to become meagre, blossoms are more seldom followed by 

 fruit; the production of a moderate crop of fruit is followed by great exhaustion, from 

 which the tree slowlj- recovers; the young shoots become more feeble and shorter; next, 

 the extremities of the branches begin todeca}"^; the fruit is now irregularly ripened, and of 

 inferior quality; mosses, lichens and canker seize upon the wood; parasites infest the 

 leaves; insects lend a helping hand in the work of destruction; birds hasten the work by 

 searching and digging for the insects; water and air are thus introduced; thus all these 

 various causes combine to reduce the aged tree to its kindred dust. All this may be ad- 

 mitted as true, yet it is contended that the decay and death of a tree are not a consequence 

 of age, or diminution of vital power, but arise from external, not intrinsic causes. " The 

 soil," LiNDLEY says, *' becomes exhausted, the roots wander into uncongenial soil, food 

 is withheld, and the elements conspire against the doomed tree." Now, there are many 

 trees and shrubs which propagate themselves considerably by means of suckers. " The 

 Aspen," Mr. Knight observes,* "is seldom seen without a thousand suckers arising 

 from its roots ; yet this tree is thinly, though universally, scattered over the woodlands 

 of England." I can speak from experience, he adds, " that the luxuriance and excessive 

 disposition to extend itself, in another plant, (the raspberry,) decline in twenty years from 

 the seed." If the diminution of vigor which precedes decay was owing to external, and 

 not to intrinsic causes, mainly, then the raspberry should go on and on, extending its cir- 

 cle each year, like the fungi of a fairy ring, never resting while there was any fresh soil 

 to occupy, and the last plants should be as vigorous as the first; for surely it cannot be 

 said that the diminution of the vigor of a plant which extends itself in this manner, can 

 be owing to the external causes above mentioned. 



In the same soil a gooseberry bush ma)' live fifty years, an apple tree two hundred, a 

 pear four hundred, and an oak one thousand. If external influences alone determine the 

 existence of a tree, why this difference.' Why does not the hardy gooseberr)', growing 

 under the same circumstances, live as long as the oak.' It is because the influence which 

 chiefly determines the existence of different species, is inherent, and not dependent solely 

 upon external circumstances. And if it is the inherent vitality or constitutional power, 

 which limits the duration of an individual tree, then, obviously, all cuttings taken from 

 that tree inherit the same constitutional power and tendencies; and the healthy existence 

 of the plants raised from the cuttings, must be nearly co-equal with that of the original 

 tree, providing it died from the infirmities of age. The truth is, the same law prevails in 

 the vegetable as in the animal kingdom. For wise purposes, difierent periods of existence 

 are assigned to different species of plants, as well as to difierent species of animals; but it 

 is obviously a law of nature, that none shall live forever. Some species of animals run 

 * Knight's Phys. and Horl. Papers, p. 84. 



