270 



VEGETABLE 



Perhaps a still more clear idea may be ob- Fig. 

 tained of the origin of branches by Fig. 239. 

 If we imagine the successive years of the 

 growth of a tree to be represented by the cones, 

 a, &, b, c, c, and d, d, then it is evident that the 

 germs producing the branches e, f, g, A, al- 

 though all of them generated on the surface of 

 a, in the spring of the first year of the plant, 

 are nevertheless, unfolded at different periods 

 of the growth of the tree. In the first year, c only becomes 

 a branch, from the surface of which springs i, which in its 



Fig. 239. 



turn gives birth to k, in the second year, g is unfolded, from 

 which grows /, the third year brings forth h, and the fourth 

 /", &c. Now in these branches the age of each is clearly 

 indicated from g, which is one year old, to e, which is four 

 years old ; but although this is the case, and/, which has ap- 

 parently sprung from an adventitious bud, is not older than A, 

 a secondary branch from e. yet the germs of all, are, in truth, of 

 the same age, having their origin on , the centre of .the trunk. 

 It. is a curious fact, that the germ of the future limb, will 

 not advance through the concentiic layers of wood, not ac- 

 tually belonging to the stem in which it originated, howev 



