T)ie Seed and its Germination 
503 
The nitrogenous material which is found in both animal 
and vegetable organisms is usually termed proteid, a word which 
has superseded the older term " albuminoid material." Proteid 
exists in several forms which differ from one another in be- 
haviour. Several great classes of proteid matters have thus 
been recognised, the albumin of white of egg, the globulins 
of blood and muscle substance, and the casein of milk being 
representatives of some of these. 
Albumin 1 is soluble in water ; globulins are soluble in water 
to which a little neutral salt, such as sodium chloride, has been 
added ; casein requires the presence of a little alkali. Albumins 
and globulins have the peculiarity of being changed by heating 
into a very insoluble form known as coagulated proteid, which 
can only be dissolved by strong acids and alkalis. Another 
class, known as " albumoses," has a peculiarity of its own, in 
that a solution of an albumose is precipitated by the addition 
to it of a drop of nitric acid, and the precipitate dissolves on 
heating the tube, appearing again as it cools. All these various 
forms, showing different degrees of solubility, agree in being 
incapable of diffusing through a membrane in the manner 
already described. There is another class which differs from all 
the others in being soluble in water, and in being capable of 
this diffusion. This is known as peptone. It is found most 
readily in the digestion of nitrogenous or proteid matter in the 
stomach of an animal, being in fact the form in which such 
proteids are absorbed in gastric digestion. 
The aleurone grains in the lupin are composed of a mixture 
of two of these proteids, an albumose and a globulin. The lupin, 
being an exalbuminous seed, stores the aleurone in grains in 
the cell of the tissue of the cotyledons, which are large fleshy 
structures exactly like those of the pea or bean (fig. 1). Before 
germination commences the grains have sharp well-defined out- 
lines, and can be seen to lie embedded in a network of protoplasm 
or living substance (figs. 12, 18). In space they take up about 
half of the cell. When germination begins they swell slightly 
as if they were absorbing water, and their enlargement causes 
the network to become compressed (fig. 19). Retaining their 
spherical shape, they begin then to lose the definiteness of their 
outline, and become studded with granules (fig. 20). They 
appear in fact to be dissolving from within outwards. The 
process of dissolution proceeds till they entirely disappear, 
leaving the cells occupied by the network of protoplasm only 
(fig. 21), which, now that the contents are expelled, is seen to 
1 This must not be confused with the term albumen, formerly used to indicate 
the endosperm— see page 492.— (Ed.) 
