102 



HISTORY OP THE VEGETABLE KINGDOM. 



fl, the episperm ; b, 

 ^ the embryo, consisting. 



named erect, as in all the synantJierece. On the 

 contrary, it is said to be reversed when it is at- 

 tached in the same manner to the summit of the 

 cell of the pericarp ; as in the dipsacem. In these 

 two cases, the trophospemi occupies the base or 

 the summit of the cell. 



The episperm, skin or pro- ''''. 



per integument of the seed, 

 is almost always single. 

 Sometimes, however, when 

 it is pretty thick, and slight- 

 ly fleshy in its interior, its 

 inner wall becomes detached 

 and separates, so that it seems 

 to be composed of two coats, 

 an outer, thicker, sometimes 

 hard and solid one, to which 

 Goertner has given the name 

 of testa, and an inner one of 

 less thickness, which is named wiien devoiopod, of 

 the teamen. This disposition "« radicle; d ti>e gem- 



•^ . ■*■ mule; £ e, the cotyle- 



is very distmctly seen m the d.)ns or lobes, 

 seed of ricinus communis; but these two mem- 

 branes are not more distinct from each other 

 than the three parts which compose the peri- 

 carp. 



The hilum is always situated upon the epi- 

 sperm. It varies in its appearance and extent. 

 Sometimes it has the form of a hardly percep- 

 tible dot. At other times, it is very large, as in 

 the horse-chestnut, in which its whitish colour 

 renders it easily distinguishable from the rest of 

 the episperm, which is dark-brown. 



Towards the central part of the hilum, some- 

 times on one of its sides, there is observed a very 

 small aperture, through which the nutritious 

 vessels pass from the trophosperm into the tissue 

 of the episperm. When the bundle of vessels is 

 continued some time before it ramifies, it forms 

 a prominent line, to which the name raphe has 

 been given. The internal point at which this 

 ends is named the internal clialaxa or umbilicus. 

 The raphe is often not easily perceptible at the 

 outside, and only discoverable by the aid of dis- 

 section, as in many eupliorhiacem ; while, at 

 other times, it is prominently and easily seen, 

 as in the genus citrus, in which it extends from 

 one end of the episperm to the other. 



In many seeds there is observed near the 

 hilum, often on the side next the stigma, a per- 

 forated organ, which Turpin has designated by 

 the name of micropyle. Some authors are of 

 opinion that the fecundating fluid makes its way 

 to the young embryo through the aperture in 

 this organ. 



j\lr Brown considers it as the base of the seed. 

 Tlie radicle of the embryo always corresponds 

 exactly to it. Previous to fecundation, the 

 ovule is composed of two membranes and a ker- 

 nel. The outer membrane, or testa, has, some- 

 times near the hilum, sometimes at a greater or 



less distance from it, a small punctifoim aper- 

 ture, which had been noticed by some of the 

 older observers, and to which M. Turpin gave 

 the name of micropyle. This aperture has no 

 direct communication with the walls of the 

 ovary. According to Mr Brown, it indicates the 

 true base of the ovule ; and the point which is 

 opposite to it, its summit. The nutritious ves- 

 sels of the pericarp, which arrive at the ovule 

 through the hilum, creep in the substance of the 

 testa until near its summit, where they form a 

 kuid of expansion communicating with the in- 

 ner membrane, and which is named the chalaza. 

 This inner membrane has a direction the reverse 

 of that of the outer, being inserted by a broadish 

 base upon the summit of the latter, the only 

 point at which the two membranes communi- 

 cate with each other. The summit of the inner 

 membrane is also perforated with a small aper- 

 ture, exactly corresponding to that in the base 

 of the testa. The kernel contained within the 

 two integuments of the ovule is a cellular body, 

 having always the same direction as the internal 

 membrane, or, in other words, is inserted at its 

 base, or the point opposite to its perforated sum- 

 mit. It consists of two parts, an outer, thick 

 and cellular part, the chorion of Malpighi ; and 

 an internal part, forming a kind of small cellulai 

 sac, often filled at first with a mucilaginous fluid. 

 This inner part is the amnios, and its fluid the 

 liquor amnii. It is in the internal sac that the 

 embryo begins to make its appearance. Its ra- 

 dicle always corresponds to the summit of the 

 kernel, or to the aperture or base of the outer 

 integument of the ovule. The endosperm, which 

 often accompanies the embryo, may be formed 

 by the sac of the amnios, or by the chorion, the 

 amnios being absorbed, or by both organs at 

 once. 



There is sometimes observed, at a greater or 

 less distance from the hiltim of sorae seeds, a kind 

 of inflated body, as in the date, the asparagus 

 and commeUna. During germination this body 

 separates, and allows the embryo to pass. 



The episperm is in general merely applied 

 upon the kernel, from which it is easily separ- 

 ated ; but, in some cases, it adheres so intimately 

 that it can be removed only by scraping it off. 

 It ne ver has cells or partitions in its interior, its 

 cavity being always simple, although, in some 

 rare cases, it may contain several embryos. 



The kernel is all that part of a ripe and per- 

 fect seed which is contained in the cavity of the 

 episperm. It has no vascular communication 

 with the episperm, unless when the two organs 

 are intimately united, in which case it is diffi- 

 cult to determine whether they may not have 

 some communication of this kind. The entire 

 kernel may be formed by the embryo, as in the 

 kidney-bean, the lentil, &c. In other words, 

 the embryo exclusively fills the -whole interna] 



