CHEMISTRY IN AGRICULTURE AND PHYSIOLOGY. 559 
becomes more or less contracted, and consequently removes 
all the contents of the cell which is inclosed in this vesicle 
from the walls of the cells. This inner wall is called the 
primordial vesicle; according to Mulder, proteine may be 
always detected in it, but no cellulose. In the centre of the 
young cell, with rare exceptions, lies the so-called 'nucleus . 
The remainder of the cell is filled with a viscid fluid con¬ 
taining an abundance of albumen . 
No plants except the fungi are without Starch. Whether 
or not starch occurs in an amorphous condition is still doubt¬ 
ful. It is likewise doubtful if it occurs in a state of solution. 
The form in which starch occurs universally is that of small 
colourless transparent granules, which are accumulated in 
the cells without definite arrangement and in variable num¬ 
bers, sometimes swimming freely in the sap, sometimes 
slightly adherent to the walls. Their size varies from an 
immeasurably small diameter to a magnitude visible even to 
the naked eye, but the maximum size of the granules of each 
plant is tolerably definite. Like the size, the form of the 
granules varies extremely in different plants, and is some¬ 
times so characteristic that, in many instances, we can deter¬ 
mine by the microscope the source whence a starch has been 
obtained. In all vegetable cells starch is a transitory pro¬ 
duct, and applied to various purposes of nutrition. Thus 
the starch disappears from the albumen of the seeds of palms 
about the period of maturation, and in its place appears 
a fixed oil, for which it undoubtedly furnishes the materials; 
it also disappears during the germination of seed and bulbs, 
serving for the nutriment of the young plant, &c. 
Certain compounds, most closely allied to starch, escape 
from microscopic observation, because they are dissolved in 
the cell-sap; these are gum and sugar. 
Sugar is very widety distributed, since it not only replaces 
starch, as in the sugar-cane, the beet, &c., but still more fre¬ 
quently precedes the deposition of starch in an organ, and 
is also formed at the solution of starch, as in trees, in the 
spring, in the germinating seeds, &c. 
The essential oils, when produced in large quantity, usually 
completely fill isolated cells and cavities which lie between 
cells. 
All plants prepare a more or less abundant quantity of 
organic acids, oxalic, malic, citric, tartaric, &c. 
In plants the fluid nutriment is taken up by absorption 
through cells. As the celFs membrane has no orifices, only 
such matters as are actually dissolved can be absorbed into 
the cells, with the w r ater which penetrate the cell’s mem- 
