president’s address. 
591 
or vegetable, is protoplasm, the only substance of the organism 
that possesses life, by which attribute it has the power of initi 
ating the various vital processes within the plant. It is generally 
of a gelatinous nature, of a highly complex composition, and 
on account of its ever-changing properties according to the require - 
ments of the metabolic processes that are always going on within 
the organism, its constitution is very unstable. The lowest form 
of organism, such as an amoeba, is simply a mass of protoplasm, 
without any cell wall, although the external surface is differentiated 
as a kind of covering. In this state it manifests all the functions 
of mobility, irritability, digestion, etc., which in the higher organ- 
isms are carried on by special structures, such as muscles, nerves, 
etc. A very important property of protoplasm, and one to which 
of late much more attention has been directed than formerly, 
is irritability, the power of responding to any external or internal 
stimulus. To this l shall refer later on. As we ascend in the 
scale, the protoplasm forms for itself a covering, the cell wall, and 
enclosed within this it is termed a protoplast, and has aptly been 
compared to a Snail within its shell. As the Snail within its 
covering carries on all the functions of life, so the protoplast by 
its contained organs develops and carries on the functions for the 
growth and sustenance of the plant. 
The living protoplast, as exemplified in an ordinary parenchy- 
matous cell, is of necessity a very complex body, possessing parts 
and organs which are of the very highest physiological importance. 
The principal organ is the nucleus, within which is a fibrillar 
network which in conjunction with two other bodies termed centro- 
spheres, act a very important part in cell division. Besides these 
are plastids one or two nucleoli and granular matter. In the main 
substance of the protoplasm, or cytoplasm as it is called, to dis- 
tinguish it from the nuclear protoplasm, are bodies termed plastids 
which when they are coloured green are termed chloroplasts or 
chlorophyll grains, and other granular matter. In a young cell 
the protoplasm with its nucleus occupies the whole interior, but 
as the cell increases in size, vacuoles occur which in the adult 
cell become merged into one. Xo increase takes place in the 
