CHAP. IV. FUNCTION OF NUTRITION. 241 



so many individual plants. The runners of the straw- 

 berry, decay when the buds at their extremities have 

 obtained a firm root in the ground, and thus the 

 parent plant becomes separated from the numerous 

 progeny scattered around it. But the closest ana- 

 logy between a plant, considered as an aggregate 

 of individuals, and any living animal, is that which 

 exists in certain marine tribes still lower in the scale of 

 organisation than the polypi to which we have referred. 

 A number of these animals are grafted and blended to- 

 gether into a compound mass, in which each still 

 possesses its separate individuality, and is capable of 

 existing in a detached form. It is by the joint labours 

 of these compound animals that a coral reef is raised 

 from the bottom of deep seas to the surface. The 

 innermost and oldest parts of the reef consist of the 

 untenanted cells of those animals which have died, 

 whilst a fresh crop is continually developing towards 

 the surface. Thus also in a tree, the oldest parts of 

 the trunk and branches is composed of matter in a dead 

 or dying state, and it is the newly developed portions 

 alone which contain the living materials capable of per- 

 forming the functions of vegetation. As these latter 

 portions originate from successive crops of fresh buds, 

 the analogy alluded to is very complete. 



It has been further observed, that if each bud be not 

 a separate individuality, we might, by grafting several 

 buds on the same stock, produce a tree composed 

 of a multitude of species ; which would be an ab- 

 surdity. 



(238.) Individuality of Plants. Any cutting, layer, 

 or bud, which has been detached from a plant, and 

 grown in an isolated state, always retains the exact pe- 

 culiarities of the individual plant from which it was 

 obtained ; but a seedling., raised from the same plant, 

 will frequently deviate more or less from the original 

 type, and present us with certain peculiarities of its 

 own. This fact appears to favour another hypothesis, 



