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such seed would be eternal also, if it were not for the many accidents 

 to which they are exposed, and which eventually destroy them. Trees 

 and other plants of a perennial nature are renovated annually ; annu- 

 ally receding from the point which was originally formed, and which 

 in the nature of things must perish in time. The condition of their 

 existence is a perpetual renewal of youth. In the proper sense of the 

 word decrepitude cannot overtake them. The Iris creeps along the 

 mud, ever receding from the starting point, renews itself as it advances, 

 and leaves its original stem to die as its new shoots gain vigour ; in 

 the course of centuries a single Iris might creep around the world 

 itself, if it could only find mud in which to root. The oak annually 

 forms new living matter over that which was previously formed, the 

 seat of life incessantly retreating from the seat of death. When such 

 a tree decays no injury is felt, because the centre which perishes is 

 made good at the circumference, over which new life is perennially 

 distributed. In the absence of accidents such a tree might have lived 

 from the creation to this hour ; travellers have even believed that they 

 had found in the forests of Brazil living trees that must have been 

 born in the days of Homer. But here again inevitable accidents 

 interfere, and the trees are prevented from being immortal. 



" Species, then, are eternal ; and so would be the individuals sprung 

 from their seeds, if it were not for accidental circumstances. 



" But plants are multiplied otherwise than by seeds. The hyacinth 

 and the garlic propagate naturally, not only by seeds, but also by the 

 perpetual separation of their own limbs, known under the name of 

 bulbs, their bulbs undergoing a similar natural process of dismember- 

 ment ; and so on for ever. The potato plant belongs to the same 

 class. Another plant bends its branches to the ground ; the branches 

 put forth roots, and as soon as these roots are established the con- 

 nexion between parent and offspring is broken, and a new plant 

 springs into independent existence. Of this we find familiar exam- 

 ples in the strawberry and the willow. Man turns this property to 

 account by artificial processes of multiplication ; one tree he propa- 

 gates by layers, another by cuttings planted in the ground. Going a 

 step further he inserts a cutting of one individual upon the stem of 

 some other individual of the same species, under the name of a bud 

 or a scion, and thus obtains a vegetable twin. 



" It is not contended, for there is nothing to show, that these artifi- 

 cial productions are more short-lived than either parent, provided the 

 constitution of the two individuals is in perfect accordance. There 

 is not the smallest evidence — it has not been even conjectured — that 



