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The Vegetable Cell had been defined as a sac or envelope, the 
wall of which was composed of a peculiar chemical substance named 
cellulose, and in its vital condition contained fluid. There had been 
some dispute with regard to this definition, because in certain lower 
forms of vegetable life provided with cilia, and floating freely in 
water, no trace of walls could be detected ; these, he considered, were 
erroneously, and, by a confusion of language, called cells. 
The physiological aspect of the cell was far more important and 
interesting than the structural, as each cell lived and performed its 
offices as an independent organ. If the petal of a flower, such as the 
pansy, were examined, it would be seen that each cell secreted its own 
colour, the same cell never secreting two different colours ; the purple 
and yellow, though appearing to blend, always being found in separate 
cells. 
Under the microscope it was not possible to show the physiological 
action, but the size, form, and relation of one cell to another could be 
exhibited. As regarded the form an infinite variety was found, caused 
by the laws of growth and external circumstances, such as pressure 
and from contiguity with other cells. 
The primary form was spherical, but the greater number were 
polygonal, and some stellate. Besides forming beautiful objects for the 
microscope, there was an interesting study in endeavouring to solve 
the question, whether the cell in its juvenile state was spherical, and if 
so, how the diverse and wondrous shapes were brought about. 
It was certain that some plants, consisting of a single cell, in 
obedience to the law of growth, took on an invariable form, which 
certainly was not spherical, though there might be exceptions. Many 
cells too, in their immature state, were devoid of. those features which 
marked them in a state of maturity, when they had taken on what was 
called secondary deposits, obtained trom the primordial uticle, or 
protoplasmic substance, spread over the interior of the cell. 
In some plants, notably the JVfe//a, examples of which he would 
exhibit, the cells were not only of very great length, but so transparent 
that the physiological action of cyclosis, or rotation of cell contents, 
was easily seen. The hairs of many plants (modified cells) also 
showed a similar state of things ; and it had been conjectured that a 
similar circulation went on in all plants, so constituting the nutritive 
process, 
