XXXIV FIRST PRINCIPLES 



482. The integuments are called collectively testa, and consist of membranes, 

 resulting from the sacs of the ovulum (399). 



483. Sometimes the testa is covered by hair-like expansions of its whole surface ; 

 as in the Cotton ; or these hairs occupy one or both ends, when they constitute 

 what is called the coma. This must not be confounded with the pappus (283). 



484. Some of these occasionally grow together, so that seeds are sometimes 

 apparently enclosed in but one or two membranes. 



485. In the seed these membranes are called by various names, of which the 

 most frequently used are spermoderm or testa, for the primine ; mesosperm, for the 

 secundine ; and endopleura for the other. 



486. All that existed in the sacs of the embryo is to be found in the integuments 

 of the seed, but in a more developed stale. 



487. The mouth of the foramen (408) is often distinctly visible, and is named the 

 micropyle. Ex. Pea. 



488. The raphe (405) occupies one side of the seed in all cases in which it pre- 

 existed in the primine ; but it frequently becomes much ramified. 



489. The raphe is in no way connected with impregnation ; its functions being 

 apparently confined to maintaining a vascular connexion between the placenta and 

 the base of the nucleus, for the purpose of nourishing the latter. 



490. Spiral vessels are found in the raphe and its ramifications. 



491. Where the vessels of the raphe expand into the mesosperm (485), the cha- 

 laza (407) appears as a discoloured thickening of the integuments. 



492. The micropyle always indicates the point in the circumference of a seed 

 towards which the radicle (412) points. 



493. And the chalaza is as constant an indication, when it is present, of the situ- 

 ation of the cotyledons (503) ; it being always at that part of the circumference 

 opposite the radicle. 



494. Between the integuments and the embryo of some plants lies a substance 

 called the albumen or perisperm. 



495. It consists of a peculiar substance deposited during the growth of the ovu- 

 lum among the cellular tissue of the nucleus (398). 



496. Care must be taken not to confound a thickening of the endopleura (485), 

 with the real albumen ; Ex. Cathartocarpus Fistula. It is probable that this is 

 often done by botanists, especially in regard to plants belonging to tribes usually 

 destitute of albumen. 



497. When the cellular tissue of the nucleus combines with the deposited matter 

 so completely as to form together but one substance, the albumen is called solid. 

 Ex. Wheat, Euphorbia. When a portion of the tissue remains unconverted, the 

 albumen is ruminated. Ex. Anona, Nutmeg. 



498. Albumen is usually wholesome, and may be frequently eaten with impunity 

 in the most dangerous tribes. Ex. Euphorbiaceae. 



499. The organized body that lies within the seed, and for the purpose of protect- 

 ing and nourishing which the seed was created, is the Embryo. 



500. The embryo was originally included within the most interior membrane of 

 the ovulum. 



501. This is usually absorbed or obliterated during the advance of the embryo to 

 maturity ; but it sometimes remains surrounding the ripe embryo, in the form of a 

 sac, which is called Vitellus. Ex. Saururus, Piper. 



502. The embryo consists of the cotyledons (503), the radicle (505), the plumula 

 (504), and the neck (506). 



503. The cotyledons represent the undeveloped leaves. 



504. The plumula or gemmula, is the nascent ascending axis (60). 



505. The radicle is the rudiment of the descending axis (60). 



506. The neck (Collet, Fr.) is the line of separation between the radicle and the 

 cotyledons. 



507. The space that intervenes between the neck and the base of the cotyledons 

 is called the cauliculus (Tigelle, Fr.) 



508. The embryo is usually solitary in the seed, but occasionally there are two or 

 several (334). 



509. When several embryos are produced within a single seed, it sometimes hap- 

 pens that two of these embryos grow together, in which case a production analogous 

 to animal dicephalous monsters is formed. 



