448 OBSERVATIONS ON THE STRUCTURE 



said to be generally the case by the most celebrated carpo- 

 logists. 



Another observation may be made, less obviously a con- 

 sequence of the structure described, but equally at variance 

 with many of the published accounts and figures of seeds, 

 namely, that the radicle is never absolutely enclosed in the 

 albumen ; but, in the recent state, is either immediately in 

 contact with the inner membrane of the seed, or this con- 

 tact is established by means of a process generally very 

 r.49] short, but sometimes of great length, and which indeed 

 in all cases may be regarded as an elongation of its own sub- 

 stance. From this rule I have found one apparent devia- 

 tion, but in a case altogether so peculiar, that it can hardly 

 be considered as setting it aside. 



It is necessary to observe, that I am acquainted with 

 exceptions to the structure of the ovulum as I have here 

 described it. In Compositse its coats seem to be imper- 

 forated, and hardly separable, either from each other or 

 from the nucleus. In this family, therefore, the direction 

 of the embryo can only be judged of from the vessels of 

 the testa.-^ And in Lemna I have found an apparent in- 

 version of the embryo with relation to the apex of the 

 nucleus. In this genus, however, such other peculiarities 

 of structure and economy exist, that, paradoxical as the 

 assertion may seem, I consider the exception rather as con- 

 firming than lessening the importance of the character. 



It may perhaps be unnecessary to remark, that the raphe, 

 or vascular cord of the outer coat, almost universally belongs 

 to that side of the ovidum which is next the placenta. But 

 it is at least deserving of notice, that the very few apparent 

 exceptions to this rule evidently tend to confirm it. The 

 most remarkable of these exceptions occur in those species 

 of Euonymus, which, contrary to the usual structure of 

 the genus and family they belong to, have pendulous 

 ovula ; and, as I have long since noticed, in the perfect 

 ovula only of Abelia.^ In these, and in the other cases in 

 which the raphe is on the outer side, or that most remote 



' Linn. Soc. Transact, xii, p. 136. ^ Abel's China, p. 377. 



