94 PHARMACEUTICAL BOTANY 
of the genus or species. They are produced by the drying up of 
protein-containing vacuoles. Each aleurone grain consists of a 
ground substance (composed of amorphous proteid matter 
soluble in water, dilute alkali or acid), in which are usually 
embedded one or more crystalloids or phyto-globulins (insoluble 
in cold water, but soluble in less than 1 per cent. solution of an 
alkali, in dilute HCl and acetic acid), one or more transparent, 
globular globoids composed of Ca and Mg phosphate (insoluble 
in water and dilute potash solution but soluble in 1 per cent. 
acetic acid solution), and frequently a crystal of calcium oxalate, 
the whole being enclosed by a protoplasmic membrane (soluble in 
water). (Fig. 53B.) 
Fic. 53.—To show Aleurone Grains. A, cells from cotyledon of seed of garden 
bean; n, aleurone grain; m, starch; B, cell from endosperm of castor bean; a, 
aleurone grain; /, ground substance; k, phytoglobulin; i, globoid. (A, After Sachs; 
B, After Frank.) 
The proteins insoluble in the cell-sap water are made soluble 
for translocation by means of proteolytic enzymes which change them 
into proteoses and peptones. 
17. MuciLacrs anp Gums are those substances occurring 
in plants which are soluble in water or swell in it, and which are 
precipitated by alcohol. 
Mucilage is formed in plants in several ways, viz.; either as a 
product of the protoplasm, as a disorganization product of some of 
the carbohydrates, as a secondary thickening or addition to the 
cell wall, or as a metamorphosis of it. In the first two cases the 
mucilage is called cell-content mucilage; in the last two, membrane 
mucilage. 
Mucilage is stored as reserve food in the tubers of Salep and 
many other Orchids and also in the seeds of some species of the 
Leguminose as Fenugreek, etc. 
