KINDS OF ALBUMEN. 341 
a. Albumen, Endosperm, Perisperm.—Those seeds which have 
the embryo surrounded by albumen, that is, by either endo- 
sperm or perisperm, or both, are said to be albwminous ; while 
those in which it is absent are exalbuminous. The amount of 
albumen will in all cases, as described above, be necessarily in 
inverse proportion to the size of the embryo. 
The cells of the albumen contain various substances, such as 
starch, albuminoids, oily matters, &c., and thus act as reservoirs 
of nutriment for the use of the embryo during the process of 
germination.. The varying contents of the cells, together with 
certain differences in the consistence of their walls, cause the 
albumen to assume different appearances in ripe seeds, and thus 
frequently to afford good characteristic marks of different seeds. 
Thus, the albumen is described as mealy, starchy, or farinaceous, 
when its cells are filled with starch-granules, as in the Oat and 
other Cereal grains ; it is said to be fleshy, as in the Barberry 
and Heartsease, when its walls are soft and thick ; or when its 
cells contain oil-globules, as in the Poppy and Cocoa-nut, it is 
oily ; or when the cells are soft, and chiefly formed of mucilage, 
as in the Mallow, it is mucilaginous ; and when the cells are 
thickened by layers of a hardened nature, so that they become 
of a horny consistence, as in the seeds of the Vegetable Ivory 
Palm and Coffee plant, the albumen is described as horny. 
These different kinds of albumen are frequently more or less 
modified in different seeds by the admixture of one with the 
other. 
Generally speaking, the albumen also presents a uniform ap- 
pearance throughout, as in the seeds of the Vegetable Ivory 
Palm ; but at other times it is more or less separated into dis- 
Fic. 763 Fic. 764. 
Fig. 763. Vertical section of the 
fruit of the Betel-nut Palm 
(Areca Catechu). c. Remains 
of perianth. jf. Pericarp. p. 
Ruminated albumen of the seed. 
é. Embryo. Fig. 764. Embryo 
of the Lime-tree (Tilia euro- 
pea). ¢, ¢ Cotyledons, each 
with five lobes arranged in a 
palmate manner. 7. Radicle. 
tinct compartments by the folding inwards of the tegmen as 
already described (see page 337). In the latter case the albu- 
men is sald te be ruminated, as in the Nutmeg and Betel-nut 
(fig. 763, p). 
b. The Embryo is the rudimentary plant, and is therefore 
necessarily present in all true seeds ; it is the fertilised oosphere 
