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-^all without much regard to the nature of the eell- 

 contents. Yet the cell- wall is. not the cell, any more than 

 the lobster shell or the crayfish shell is the lobster or the 

 crajrfish. 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 a cell- 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 Kemer 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. 



178 



