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SECOND BOOK. 

 ON THE PLANT-CELL, 



CHAPTER I. 



FORM OF THE PLANT -CELL. 



SECTION I. 



THE CELL REGARDED AS AN INDIVIDUAL. 



14. ONLY in a fluid (cytoblastemd] containing sugar, dextrin, 

 and mucus (protein), can cells be formed. This is effected in two 

 ways : 1st. The particles of the mucus are drawn together into 

 a more or less rounded body, a cell-kernel (cytoblastus), and change 

 the entire surface of one part of the fluid into jelly, a relatively in- 

 soluble substance. Thus originates a closed gelatinous vesicle, into 

 which penetrates the external fluid, and distends it, so that the 

 mucus-corpuscle on one side is free, and on the other remains 

 adherent to the inner wall of the vesicle or cell. It forms then a new 

 layer on its free side, and is thus enclosed in a duplicature of the 

 wall ; or it remains free, and is then mostly dissolved and disappears. 

 During the gradual extension of the vesicle the jelly of the wall is 

 commonly converted into cellulose, and the formation of the cell is 

 completed. 2d. The collective contents of a cell are divided into 

 two or more parts, and around each part there is immediately 

 formed a tender gelatinous membrane. In this way many cells 

 are formed, which fill up the cell in which they originated. 



Of the nature of the fluid in and out of which the cells originate, we 

 are not yet perfectly cognisant. Thus much we know, that in some cases 

 (in the embryo-sac of the Leguminosce, for instance) a solution of sugar is 

 present ; and, as far as may be decided by the action of alcohol, this is 

 mixed with gum (dextrin ?). The constant presence of a nitrogenous 

 substance is also necessary, and which we should have anticipated from 

 previous considerations ( 11.). 



In all tender hairs, almost in every growing portion of cellular tissue, 



