4 
HISTOLOGY OF VEGETABLES. 
the two kingdoms the individual cell belongs, since it 
possesses characters common to both. Zoologists, 
botanists, and chemists, have, each and all, bestowed 
the labour of years on the solution of this question, 
and have endeavoured, but without success, to establish 
some decisive character by which animals and plants 
may be distinguished. 
In the earlier periods of natural history, the power 
of spontaneous motility, and the presence of a stomach, 
were considered as the distinguishing characteristics of 
an animal. It is now well known that certain con- 
fervae possess the power of locomotion, while the 
sponges and some allied families of animals, are desti- 
tute of both these attributes. Chemists in former times, 
considered the presence of nitrogen as a distinct proof 
of the animal character of the tissues containing this 
element ; but more modern researches have demon- 
strated that nitrogenized matter is a necessary consti- 
tuent of the growing parts of plants. Histological 
inquiry, as I have already stated, has proved equally 
incapable of solving this question ; the appeal to the 
higher powers of the microscope having rendered the 
problem more complex by the discovery of a common 
in place of a distinctive character ; namely, the primary 
cell, or starting point for all organic beings. 
It being demonstrated by histological examination 
that the cell is the primordial condition of the animal 
and the plant, it is essentially necessary that the 
student of histology should be himself familiar with 
