38 
black alone, viz., by furnishing a more plentiful supply of tbe myrosin for 
the decomposition of tbe myronate of potassium in tbe black seeds. It 
may be observed that the white seeds have a slightly sharp taste but this 
is caused by the action of the myrosin upon another salt called the 
sulpho-cyanide of sinapin. It is an acrid but not a volatile principle. 
The structure of the white mustard seeds is most interesting under 
the microscope, and essentially different from that of the black. The 
seeds have a husk built up with three layers of cells or tunics. The 
exterior tunic consists of a transparent series of hexagonal cells tF§in. 
broad, and §■ Join, long, and united to each other by a corrugated cell wall. 
In the centre of each is an aperture surrounded by an elastic spiral fibre 
from which a long tube passes from the interior to the exterior. When 
wetted with water this elastic apparatus springs forward, projecting from 
the surface like the school-boy's " jack-in-the-box," carrying with it the 
tube from which flows a thick mucilaginous fluid. It is distinctly 
different from the well-known spirals of the Collomia, but rather 
resembles the cushion springs of the upholsterer, covered with an 
exceedingly fine membrane. It is best seen by the aid of polarized light 
and a blue selenite stage. This curious compound cell is totally absent in 
the black mustard seeds. The other two tunics are simply layers of 
irregular cells. The interior of the seed is composed of cells containing a 
large quantity of the fixed oil. There is no starch in any part of the 
seeds, therefore if any effect is produced on Iodine an admixture of wheat 
or some other flour will be readily detected. 
The white mustard is of more recent introduction than the black, and 
almost any soil is adapted for its growth. An average yield is from 30 to 
40 bushels of 50 pounds each per acre, the usual price being nine and 
sixpence per bushel. 
The chemical nature of the essential oil of mustard recalls to our 
thoughts a singular fact in the history of the human race. Many 
nations having no connection with each other and having no means of 
communication have instinctively chosen certain plants as food which 
although totally differing in outward appearance, all contain a 
chemical principle identical either in composition or qualities. Thus for 
instance in the eastern hemisphere the Chinese have their favorite tea 
and the Arabian his coffee. In the western hemisphere the Brazilian has 
his holly and the Mexican his cocoa. All these vegetables contain thein, 
or a similar substance. They, like the modern Australian gold-digger, 
without knowing the reason why, found out that an infusion containing 
