248 MR. MIERS ON THE STRUCTURE OF THE SEED 



with the raphe through the diapyle * or aperture in the testa, constitutes an important 

 feature in this inquiry. The nipple-shaped protuberance in the summit of the nucleus, 

 hitherto taken to be the radicle, appears to me, without the smallest doubt, as was first 

 shown by Richard, to be the two cotyledons of the embryo, which, although small and 

 short, are nevertheless quite distinct, and their relative position is indicated by the direc- 

 tion of the cleft, being placed right and left of the axis, or with their commissure pointed 

 to the raphe : the main body of the nucleus, instead of being the confluent cotyledons, as 

 hitherto supposed, must be a gigantic radicle, in the axis of which is imbedded the caulicle 

 of the embryo, shown in the opake central line previously mentioned, terminated at its 

 base by the shining speck before described, and at its apex by the plumule, which is seen 

 protruding into the space at the bottom of the cotyledonary cleft. The minute external 

 speck, which I consider to be the germinating point of the caulicle, is always more or less 

 prominent, and of a green colour in the living state : this point does not exactly corre- 

 spond in position with the micropyle of the testa, but is somewhat lateral in respect to it, 

 and nearer the basal origin of the raphe. 



Although this axile portion of the radicle is plainly distinguishable in numerous other 

 less prominent cases, it has never been distinctly noticed. In Pekea the superiorly 

 exserted portion of this process has been called the caulicle t, a name also given to the 

 large germinating protrusion in the embryo of Rhizophora, but inappropriately, because 

 that term is applicable only to the ascending system, or the elongating portion of the 

 plumule above its junction with the cotyledons : all below this point belongs to the de- 

 scending system, and in order to distinguish it from the main radicular mass, it may be 

 called the neorhiza : it is in fact the growing portion of the elementary root, the more 

 external mass of the radicle being inert, or at least serving only the purpose of albumen 

 or of large fleshy cotyledons, in affording nutriment to the germinating parts of the 

 embryo %. 



* This word is proposed to denominate the distinct aperture often seen pierced through the substance of the osseous 

 testa, and by which the raphe penetrates, to unite with the chalaza of the tegmen or inner integument of the seed, and 

 is used in contradistinction to the foramen, a term applied to the orifice of the primine of the ovule, which afterwards 

 becomes the micropyle of the seed : this last, in seeds produced from anatropal ovules, is situated at the extremity 

 always opposite to that in which the diapyle is placed. In the case of Clusia above detailed, the diapyle is a very 

 manifest aperture, filled with soft fungous matter ; in some other cases it is closed by the osseous deposits of the te3ta, 

 and is only recognizable as the point where the extremity of the raphe, when it is free, penetrates the testa. This 

 must not be confounded with the omphalode, a term applied by Turpin to express the aperture in the centre of the 

 hilum in antitropal seeds through which the nourishing vessels pass to promote the growth of the embryo ; nor with the 

 caruncula, a name used to express indiscriminately any excrescence or swelling upon the testa, whether about the 

 strophiole, about the hilum, or about the micropyle, where, according to St. Hilaire, it is sometimes observed, as in 

 Euphorbia, Ricinus and Polyyala. 



f This term (synonymous with the tigelle of the French botanists) is vaguely applied by some authors : thus Gau- 

 dichaud (Recherches sur l'Organographie, &c. p. 39) defines " la tigelle, ou ce qu'on nomme ordinairement la radicule 

 dans les embryons ; cette partie sert a la composition des tiges." By this is evidently meant only that ascending 

 portion of the collar of the embryo, which I have above defined as the true caulicle, and which does not belong to the 

 radicle, although continuous with it. 



% It may be maintained by some, that Gcertner's view is correct in considering the great body of the radicle as an 

 albumen, and the neorhiza as the radicle, both agglutinated into one mass ; but this argument will not hold good, 



