CHAPTER V 
VEGETABLE CYTOLOGY 
Vegetable Cytology treats of plant cells and their contents. 
THE PLANT CELL AS THE FUNDAMENTAL UNIT 
Schleiden, in 1838, showed the cell to be the unit of plant structure. 
The bodies of all plants are composed of one or more of these funda- 
mental units. Each cell consists of a mass of protoplasm which 
may or may not have a cell wall surrounding it. While most plant 
cells contain a nucleus and some contain a number of nuclei, the 
cells of the blue-green algae and most of the bacteria have been 
found to lack definitely organized structures of this kind but rather 
contain chromatin within their protoplasm in a more or less diffuse 
or loosely aggregated condition. 
A TYPICAL PLANT CELL 
If we peel off a portion of the thin colorless skin or epidermis from 
the outer convex surface of an onion bulb scale, mount in water and 
examine under the microscope, we find it to be composed of a large 
number of similar cells which are separated from one another by 
means of lines, the bounding cell walls. Under high power each of 
these cells will exhibit the following characteristics: 
An outer wall, highly refractile in nature and composed of cellulose 
which surrounds the living matter or protoplasm. This wall is not 
living itself but is formed by the living matter of the cell. Some- 
where within the protoplasm will be noted a denser-looking body. 
This is the nucleus. Within the nucleus will be seen one or more 
smaller highly refractile and definitely circumscribed bodies, the 
nucleolus or nucleoli. The protoplasm of the cell outside of the 
nucleus is called the “cytoplasm.” It will be seen to be clear and 
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