ye 34 
cellulose is formed outside the primordial utricle of the — 
protoplasm by the solidifying of a more or less fluid sub- 
stance which is excreted from the protoplasm. ee? 
The formation of cells by ced/-diviston is far more common — . 
than that by free cell-formation, since it alone takes place 
in all those processes which depend on normal growth. ; 
In this process the protoplasm of the mother-cell separates — 5 
into several portions, which generally fill up the mother-cell 
SO completely that no more space is left than is sufficient 
Structural and Physiological Botany. 
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Fic. 55 II.—Free cell-formation in the embryo-sac Fic. 56.—TIwo- cells of 
of the scarlet-runner; @ a cells already perfect. SAtrogyra in the act of 
(x 670.) division, after contraction 
of the cell-contents by the addition of a solution of sugar, the portions of the cell- 
wall already formed being thus made visible. In each half of the cell is a 
secondary nucleus from which bands of protoplasm proceed to the margin. 
(Strongly magnified.) 
for the production of cell-walls. In certain cases, in which 
the membrane is formed gradually, the division of the proto- 
plasm into its separate portions, which advances from the. ee 
outside of the cell towards the centre, is accompanied part ~ 1 
passu by the formation of the cell-wall. This first makes its - _ 
appearance as a narrow ridge on the inner surface of the “ 
original cell, which gradually increases in breadth until at 
length it has divided the entire cell-cavity intocompartments. _ 
