CHAPTER XII 
PROTOPLASM AND ITS PROPERTIES 
191. The Cell in its Simplest Form. — Sufficient has 
been said in the preceding chapters, and enough tissues 
have been microscopically studied, to make it pretty clear 
what vegetable cells, as they occur in flowering plants, 
are like. In Chapter XI, leaf-cells have been taken for 
granted and their work described in some detail. Before 
going further, it is worth while to consider the structure 
of an individual cell, and to see of what kinds of activity 
it is capable. 
In studying the minute anatomy of bark, wood, pith, 
and other tissues the attention is often directed to the 
cell-wall without much regard to the nature of the cell- 
contents. Yet the cell-wall is not the cell, any more than 
the lobster shell or the crayfish shell is the lobster or the 
crayfish. The contained protoplasm with its nucleus is the 
cell! ‘The cell reduced to its lowest terms need not have 
a cell-wall, but may consist simply of a mass of proto- 
plasm, usually containing a portion of denser consistency 
than the main bulk, known as the nucleus. 
Such cells, without acell-wall, are not common in the vege- 
table world, but are frequently encountered among animals. 
192. The Slime Moulds.?— One of the best examples of 
masses of naked protoplasm leading an individual existence 
1 See Kerner and Oliver’s Natural History of Plants, Vol. I, pp. 21-51. 
2 Strasburger, Noll, Schenk, and Schimper’s Text-Book of Botany, pp. 50-52 
and 302-305. 
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