216 HOW PLANTS GROW. 



distinctive physiological character was the power to manufacture 

 "protein" from less complex materials. 



In our present study, we must keep two main facts promi- 

 nently and clearly before us : — First, that all plant-growth goes on 

 by intussusception, not by accretion ; second, that we are dealing 

 with organisms whose elemental parts — i.e.^ their cells — possess 

 walls made of cellulose, and who are able to exercise this manu- 

 facturing power, in virtue of which they make their cellulose, and 

 all the other important chemical substances intimately connected 

 with their " growth." 



These points being clear, I purpose to sketch in this paper the 

 methods by which plants increase, and, as a type, to trace the 

 growth of an ordinary flowering-plant from the very first cell of 

 the embryo — />., the initial result of the process of fertilization up 

 to the adult plant, with its various organs. 



It is difficult to show how this first embryonic cell comes about 

 without trending in the direction of reproduction. It is equally 

 difficult to trace the after-steps of development without going too 

 deeply into the question of the food of plants, its uses, and the 

 manner in which it is taken in — in a word, the processes of 

 assimilation and nutrition. Therefore, I shall only say so much 

 concerning reproduction as will suffice to define the posiiio7i of the 

 primary embryo cell, and only so much about food and assimila- 

 tion as may be needful to show the necessity that exists for the 

 food to be used by the plant, and to demonstrate the function of 

 certain organs, which must be named. How plants feed, move, 

 climb, and reproduce, are subjects worthy of separate papers, 

 which may at a future time appear in this Journal. 



I.— The Vegetable Cell. 



We shall, first of all, discuss the simple plant-cell : its composi- 

 tion, contents, form, varieties, and so forth. Having seen it in 

 its initial stage, as the starting-point of the embryo, and discussed 

 the method by which it managed to assert its right to exist at all, 

 we shall trace its development into tissues and organs^ making up 

 the adult plant. 



Take as the primary and all-important axiom of plant-life this : 

 All k7iGwn plants consist wholly of either o?ie cell, modified i?i various 

 ways in different cases, or of a number of cells, greater or smaller^ 

 viodified in almost endless variety. 



