ROOT AND STEM, 



61 



F.g. 3^5". 



F^'g. '5H^. 



P'g-.^^^^ 



F'g.3v6A, 



-5C 

 P 



F. 



S*^*'^ 



Rg.3v^Rg.3//8. 7|V/ <3*50. 



Fig». 35-|. 



Finally, the pharmacognosist will find and its form not yet perfect. Its analogy 



it of importance in the case of seeds pos- 

 sessing a characteristic taste to inform 

 himself as to the part, if any, to which 

 such taste is restricted. 



With the production of the seed, con- 

 taining a distinct living individual sej)- 

 arated from the parent and fitted for in- 

 dependent existence, reproduction can 

 strictly be considered as completed, al- 

 though the progeny is still in its infancy 



to the bud is apparent. Each consists of 

 one or more vegetative units ready to de- 

 velop under proper conditions into a per- 

 fect semblance of the parent, and each is 

 provided with a store of prepared nour- 

 ishment to sustain it until able to manu- 

 facture such for itself. The distinction 

 is in the radically different modes of 

 origin and in the structure, leading to dif- 

 ferent powers of reproduction. 



GENERAL STRUCTURE OF ROOT AND STEM. 



The development of the embryo com- 

 mences with the division of the fertilized 

 oosphere into two cells, each of which 

 grows and becomes capable of itself di- 

 viding similarly. The result of such cell 

 propagation, is the production of a tissue 

 and of a body which becomes elongated 

 through successive transverse divisions 

 of its cells, or certain of them, and broad- 

 ened by their longitudinal division. So 

 long as the cells produced are the same 

 in kind the body consists of but one tissue; 

 but through differentiation and specializa- 

 tion among them different tissues are soon 

 developed. The power of cell-division 

 and growth is lost by most tissue after a 



time, while in other parts it persists per- 

 manently. Any tissue or portion of tissue 

 which possesses such power is called 

 Meristem or Meristematic Tissue. Tis- 

 sue may cease finally to exert meris- 

 tematic power, or it may resume such 

 power after a time. All meristematic 



processes cease upon maturity of the 

 seed, recommencing with germination. 

 The point reached in the development of 

 any plant-body in the embryonic condi- 

 tion — that is, at the maturity of the seed- 

 does not depend in any degree upon the 

 amount or kind of tissue or tissues de- 

 veloped, but altogether upon the habit of 

 the particular plant. In some embryos 

 tissue differentiation cannot be seen to 

 have taken place at the time of separation 

 from the parent, while in others it has 

 progressed very far, though never (unless 

 germination has occurred) to the produc- 

 tion of a true root. It is impossible, +here- 

 fore, to fix upon any particular develop- 

 mental stage of stem structure as distin- 

 guishing the ungerminated embryo from 

 the germinated plantlet. In the following 

 sketch of its development, then, no note 

 is taken of the resting period in the seed 

 state, but the process is followed as 

 though it were continuous from fertiliza- 



