-CHAPTER XIII. : 
- Protoplasm and its Properties.! 
‘160. 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 vege- 
table cells, as they occur in flowering plants, are like. But 
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 
protoplasm is the cell.2 The cell, reduced to its lowest terms, 
need not have a cell wall, but may consist simply of a mass 
of protoplasm, usually containing a portion of denser con- 
sistency than the main bulk, known as the nucleus. 
Such cells, without a cell wall,-are not common in the 
vegetable world, but are frequently met with among animals. 
161. The Slime-Moulds.? — The best example, among plants, 
of masses of naked protoplasm leading an individual exist- 
ence is found in the slime moulds, which lve upon rotten 
tan bark, decaying wood, and so on. These, like most flower- 
less plants, spring from minute bodies called spores, Fig. 102, a, 
which differ from the seeds of flowering plants, not only in 
11f the teacher prefers to complete the study of the structure and functions of 
flowering plants before taking up lower forms, he may omit the present and the 
following chapter until after the flower and the fruit have been studied. It seems 
better to the author, however, to introduce the morphology and physiology of cells 
as individuals pretty early, and there are many reasons for taking up these topics 
immediately after Chapter IV. 
2 See Kerner and Oliver’s Natural History of Plants, vol. I, pp. 21-51. 
3 Strasburger, Noll, Schenk, and Schimper, Lehrbuch, pp. 42, 43 and 260-263. 
