9 6 CELL-CONTENTS. [CHAP. 



elements of water, oxygen, and hydrogen, forming a ter- 

 nary compound (celhilose). The essential part of the cel!- 

 contents consists of the same elements combined with 

 nitrogen and sulphur, constituting protoplasm. Wherever 

 we have growth going forward, there we have the proto- 

 plasmic cell-contents, in varied association with water, in 

 activity. 



In the living-cells of all flowering-plants may be dis- 

 cerned, under sufficient magnifying power, a minute por- 

 tion of the protoplasm segregated in the form of a rounded 

 or lens-shaped, more or less distinctly defined body, em- 

 bedded in the protoplasmic contents. In many Monoco- 

 tyledons (Hyacinth, Spiderwort, Orchis) it may readily 

 be found, from its unusual relative size, especially in the 

 epidermal cells. This is the so-called cell-nucleus or 

 cytoblast, and the focus, so to speak, of protoplasmic 

 activity. 



The way in which growth in plants takes place is 

 simply this. The contents of the cells of the growing 

 part, following an immediately antecedent fission of their 

 cell nuclei, divide in two, and between the halved contents 

 there forms a thin layer of the ternary cell-wall, which 

 divides each cell into two distinct cells. The new cells 

 then increase in size until they become as large as their 

 parent cell, when they each divide again, and the process 

 is repeated. With this increase in superficies of the cell- 

 wall is associated an increase in thickness to a greater or 

 less extent, though the activity of the thickening process 

 usually attains its maximum after the cell has attained 

 its full size. As a general rule, long and tapering cells 

 acquire very thick walls, while short cells remain per- 

 manently thin, or become thickened according to 

 circumstances. 



7. CHLOROPHYLL. If you take any green part of a 

 plant (and it will be best to take a morsel from some succu- 

 lent leaf, or the thin leaf of a moss), and examine the cells 

 under a powerful microscope, you will find that the entire 

 cells are not coloured green, neither are the whole of the 

 cell-contents, but that the colouring matter is limited to 

 very minute granules of protoplasm lying in the colourless 

 fluid contents. These are called the chlorophyll granules. 

 The development of the green colour of these granules, 



