CHEMICAL BASIS OF PLANT FORMS 243 
has been found to be due to the imperfect development of the 
tissue and not to an insufficient supply of silica. 
The percentage of ash-constituents in plants varies, but the 
quantity is sufficient to be a very important factor in the con¬ 
sideration of chemical forms of plants. 
I have already said that the albuminous cell contents, called 
protoplasm, are always present in the living cells of plants. The 
introduction into the cell of the gases, water, and inorganic sub¬ 
stances goes to the direct formation of this colloidal body, or 
assists in it. 
It has been stated that the soil, water, and atmosphere supply 
the food of all plants. It would be of interest to dwell upon the 
processes of assimilation and the chemical changes that go on 
within the living plant, if our time would allow. It may be men¬ 
tioned that nowhere in any department of chemistry have our 
former views been more modified than in the physiological 
chemistry of the vegetable cell during the last three years. 
For example, I may say that, at least in some plants, nascent 
starch passes in a soluble form from cell to cell by osmosis with¬ 
out conversion into sugar, as was formerly held. 
Sugar in some plants may be regarded as a waste product, 
resulting from the breaking down of more complex substances, 
of no further service in the development of the plant. 
Sorghum 1 cane, at the time of the maturing of the seed and 
the full growth of the plant, contains the largest percentage of 
sugar, and this sugar appears to be really a waste product. 
The classification of Plastic and Waste Products , in Vines’s 
late Physiology , 2 cannot be accepted as final, since many changes 
in plant chemistry have resulted since 1882 —the date of his 
chemical bibliography. 
It may be generally said that the proteids or albuminoid sub¬ 
stances are formed in the cell from a simple carbohydrate and 
some nitrogenous body, probably an amide. 
The inorganic acids supply sulphur and other substances 
necessary to enter into combination with the proteid, or act 
mechanically by removing waste material. 
1 H. W. Wiley, Botanical Gazette, 1887. 
2 Cambridge edition, 1886. 
