164 VEGETABLE PHYSIOLOGY 
albumin. There is no evidence at present that they are 
stages in the constructive process. 
Some of the proteoses occur in certain seeds in associa- 
tion with some of the globulins. Both the albumins and 
the globulins, and probably the meta-proteins as well, are 
transformed into proteoses and peptones by the action of 
hydrolysing agents, such as dilute mineral acids and certain 
secretions of the protoplasm known as enzymes, whose 
action will be treated of in a subsequent chapter. 
Besides these classes of proteins, another occurs which 
presents the curious peculiarity of being soluble in alcohol. 
Proteins of this group have been extracted from the endo- 
sperm of some of the cereal grasses. Examples of them 
are found in the zein of maize; and the gliadin and 
glutenin of wheat flour. Zein differs from the crystallised 
protein of the hemp in its comparatively low content of 
nitrogen, which amounts to only 16°13 per cent. It dissolves 
easily in alcohol of about °820 specific gravity, but is 
insoluble in absolute alcohol. It is insoluble also in water, 
but in mixtures of alcohol and water it dissolves to a 
greater or less extent, being most easily soluble in a mixture 
containing about 90 per cent. of the spirit. In one of a 
lower concentration than 50 per cent. it is very sparingly 
soluble. Zein can be dissolved by glycerine if heated to 
150° C.; also by glacial acetic acid and by dilute solutions 
of caustic potash. Like other proteins, it is converted into 
peptone by pepsin and hydrochloric acid. 
The original construction of protein matter, like that 
of carbohydrates, seems to be carried out only by 
vegetable protoplasm. It does not, however, appear to be 
dependent upon the same conditions as the process already 
described. It cannot be classed with the latter as a process 
of photosynthesis, and it is only indirectly dependent 
upon the action of the chlorophyll apparatus. Unlike the 
construction of carbohydrates, it is not confined to green 
plants—indeed the fungi can commence the synthesis at a 
lower stage than the latter, beginning the construction with 
