118 



LETTERS ON TREES. 



by the extension of internodes, the foliar merithals frequently 



Fig. 14. 



become alternate. A Dicoty- 

 ledonous plant may be consi- 

 5^-c:^i>> dered as consisting of a series 

 '^'d Qiphytons (Fig. 14), which pro- 

 duce an ascending foliar sys- 

 tem, and a descending radicu- 

 lar one," — [the series being 

 arranged one above and outside 

 the other.] 



In the phytons or foliar 

 types of these two great classes 

 of plants, cells and vessels of different kinds are united ; and 

 the phytons may be considered, in reference to the entire 

 plant, precisely in the same way as the simple cell is regarded 

 when compared with the various tissues forming the compound 

 individual. A phyton may be thus regarded as an organ 

 furnishing a type of all the parts which enter into the com- 

 position of the nutritive and reproductive compound organs. 

 While the embryo of phanerogamous (or flowering) plants may 

 be considered as a phyton produced by the process of repro- 

 duction^ the hud may be reckoned a phyton produced by the 

 vegetative process. A bud has a certain degree of vitality 

 inherent in itself; and it may be called a fixed embryo^ or one 

 attached to the plant, and depending for its vigour upon it, but 

 frequently capable of gi'owing when separated from it." 



15. IN'ow observe what Professor Balfour says 

 further : 



A tree is composed of a series of buds, each having inde- 

 pendent vitality, and yet all united on a common axis, on the 

 life of which they depend for their continued growth and 

 vigour. Buds may be taken from one tree and grafted upon 

 another, and, in some instances, buds, or bodies equivalent to 



