CHAP. II. ALBUMEN AND EMBRYO. 211 



bertia voliibilis and Euonymus eiiropaeus, 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 inteo-u- 

 ment is called the nucleus; and consists either oi albumen and 

 embryo, or of the latter only. 



The albumen {perispermium, Juss.; endosperminm, Rich.; 

 medulla seminis. Jungius; secundince internee, Malpio-hi) 

 (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 Annonacese 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. I. b, &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 Avithin 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 



