CHAPTER II 
THE TISSUES OF PLANTS 
HISTOLOGY 
36. In many groups of plants a single cell makes up 
the whole plant. In such groups the cells may vary 
considerably in different species but there is not possible 
a differentiation into cells of different structure for differ- 
ent functions. All of the normal activities of the plant 
are carried on by the same cell and, therefore, the modi- 
fications of the cell are limited to those that do not inter- 
fere with any of these functions. Aside from these 
limitations the cell may vary much in size, shape, struc- 
ture of wall, location and size of nucleus and vacuoles, 
etc. 
37. In other forms of plants there are several to many 
cells forming one plant in which all of the cells are 
essentially alike and each capable of continued existence 
by itself even if the others should be destroyed. Sucha 
plant is scarcely more than a group of nearly independent 
individuals. As we study the more and more complex 
forms of plants, however, we find that the cells are no 
longer all alike or nearly so, but that some are different 
from the others in shape, structure and function. The 
cells are not all equivalent, the plant is not now a collec- 
tion of nearly independent individual parts (cells) but 
the whole must be considered as an individual made up 
of numerous differentiated parts. It is true that in the 
history of every plant there occurs a one-celled stage and 
27 
