CHAP. II. 
ALBUMEN AND EMBRYO. 
211 
bertia volubilis and Euonymus europseus, in which it is of 
unusual dimensions, it is scarcely visible in the unimpregnated 
ovary ; and it is stated by Brown, that he is not acquainted with 
any case in which it covers the foramen of the testa before im- 
pregnation. 
The mass enclosed within the true testa or outer integu- 
ment is called the nucleus ; and consists either of albumen and 
embryo^ or of the latter only. 
The albumen (perispermium, Juss.; endospermium, Rich.; 
medulla seminis, Jungius; secundince internee^ Malpighi) 
(Plate VI. fig. 5. a, 1. a, 9, a, &c.), when present, is a body 
enclosing the embryo, and interposed between it and the in- 
tegument of the seed : it is of various degrees of hardness, 
varying from fleshy to bony, or even stony, as in some palms. 
It is in all cases destitute of vascularity, and has been usually 
considered as the amnios in an indurated state : but Brown is 
of opinion that it is formed by a deposition or secretion of 
granular matter in the cellules of the amnios, or in those of 
the nucleus itself. The albumen is often absent, frequently 
much smaller than the embryo, but is also occasionally of 
much greater size. This is particularly the case in monoco- 
tyledons, in some of which the embryo scarcely weighs a few 
grains, while the albumen weighs many ounces, as in the 
cocoa-nut. It is almost always solid, but in Annonaceae and 
the nutmeg tribe it is perforated in every direction by dry 
cellular tissue, which appears to originate from the remains of 
the nucleus in which the albumen has been deposited : in this 
state it is said to be ruminated. 
The embryo (or corculum) (Plate VI. fig. 1. 5, &c.) is a 
fleshy body, occupying the interior of the seed, and consti- 
tuting the rudiment of a future plant. It is usually solitary, 
but there are instances of the presence of several in one seed. 
It was originally developed within the innermost membrane of 
the ovule. In most plants one embryo only is found in each 
seed. It nevertheless occurs, not unfrequently, that more 
than one is developed within a single testa, as occasionally in 
the orange and the hazel nut, and very commonly in Coni- 
ferae, Cycas, the onion, and the mistletoe. Now and then a 
union takes place of these embryos. 
p 2 
