214 O' Brien . — The Proteids of Wheat. 
found that these grains contain the double phosphate of 
calcium and magnesium, characteristic of globoids. He there- 
fore considered that the aleuron -grains of Gramineae are in 
every respect normal, consisting of a small peripheral layer 
of proteid, and an exceptionally large globoid. Of the proteid 
substance he does not treat, beyond mentioning the observa- 
tion that it dissolves in potash, setting free the globoid. 
The following work was undertaken in 1893, at the 
suggestion of Professor Vines, in order to try to complete 
our knowledge of the aleuron-grains of the Gramineae with 
some account of their proteid constituents. It will be seen 
that my observations chiefly agree with those of Liidtke, 
in part combining his results with those of Mr. Groom. 
The Aleuron- Layer of Wheat. 
The constitution of the aleuron-layer of the Gramineae has 
been frequently described. Whilst in most starch-containing 
seeds starch and aleuron-grains occur together throughout 
the endosperm, the aleuron-grains are here confined to its 
specialised outer layers, starch to its central mass. 
In Wheat the aleuron-layer is in most places but one cell 
thick, and is protected externally by a strongly cuticularised 
layer of the testa. The continuity of protoplasm from cell to 
cell may easily be seen in a thickish section without other 
preparation than careful staining in Hoffmann’s blue and 
mounting in glycerine. On treating a section with absolute 
alcohol, and then with concentrated sulphuric acid, a per- 
sistent pink protoplasmic network shows continuity between 
the aleuron-layer and the rest of the endosperm. The 
immediately underlying cells are specially rich in proteid 
matter (gluten) ; their starch-grains are somewhat larger than 
the aleuron-grains and are fairly regular in size. Most of the 
endosperm-cells, however, contain large circular flattened 
starch-grains, the interstices between which are so densely 
packed with minute, often angular starch-grains, that the 
proportion of gluten is small. 
