LETTER XI. 



117 



whence roots are produced. This phyton is capable of pro- 

 ducing others having a similar constitu- 

 tion ; and thus a more complicated Mo- 

 nocotyledonous plant consists of a series 

 of phytons placed one above another, the 

 parts being alternate (as seen in the 

 adjoining figure, Fig. 12). Each phyton 

 has a distinct leaf, producing a bud in its 

 axil, or at the part where it is united to 

 the axis : it has also an ascending or 

 foliar, and a descending or radicular 

 system. In the case of the first phyton, the latter descends at 

 once into the soil ; but in the case of 

 the others, it passes downwards through 

 the first axis^ before it reaches the 

 ground, or in some instances it appears 

 externally at the base of the phyton, 

 and thus becomes for a time aerial (r, /). 

 A Monocotyledonous plant may thus be 

 said to consist of a series of phytons, 

 arranged one within [and above] the 

 other, with shortened axes. 



A Dicotyledon (or Exogen), on the 

 other hand, in its simplest state, may be said to consist of an 



Fig. 13. 



axis producing two leaves at its 

 summit and roots below (Fig. 13). 

 It may be represented as two 



hytons united, the foliar meri- 



iials (c d) being placed opposite 



0 each other. In the Monocoty- 



edon, each node produces one leaf 

 and is unifoliai' ; in the Dicotyledon, two, and is bifoliar. 

 This tendency to produce two leaves at a node does not, 

 however, remain permanently in all Dicotyledons ; for, 



