166 Dr. Giraud's Contributions to Vegetable Embryology. 



apex, with which, however, it is brought in contact at a subsequent period, 

 and ultimately even penetrates that membrane ; so that, in this instance at 

 least, the primary utricle cannot result from a depression or involution of the 

 embryo-sac, as is maintained by Adolphe Brongniart. 



After the expansion of the lobes of the stigma and its impregnation, the 

 pollen-tubes may be traced in the conducting tissue of the style, but not so far 

 as the micropyle : in the channel, however, leading to this point, the pollen- 

 granules are found in abundance, and are doubtless brought in contact with 

 the outer surface of the embryo-sac through the exostome and the minute 

 canal in the apex of the nucleus. 



At this period the first trace of the embryo appears in the formation of the 

 spherical body at the inferior extremity of the primary utricle, which has now 

 assumed the character of the suspensor {umbilical cord). Hence, then, we are 

 led to consider the origin of this simple spherical body, which is ultimately 

 transformed into the embryo, as resulting from a peculiar process of nutrition, 

 determined by the material or dynamic influence of the fovilla, conveyed 

 through the medium of the primary utricle or suspensor. As it is through 

 that organ that the embryo appears to derive its nourishment during the 

 period of its development, we should from this function, as well as from its 

 anatomical relations, consider the suspensor as the true umbilical cord ; the 

 medium of connexion, therefore, between the ovule and the columella (or so- 

 called placenta) ought not to receive the name of umbilical cord or funiculus, 

 which terms it would be well to confine to the suspensor alone ; while the 

 former might retain the appellation of podosperm, as referring to its relation to 

 the ovule. 



As it is necessary that an umbilical cord should be organically united with 

 the embryo, the impropriety of considering the organ described by Malpighi 

 in that light will become sufficiently obvious. This structure consists of a 

 minute cellular process extending from the base of the embryo-sac to the base 

 of the nucleus, and has been found chiefly in the Cucurbitacece and Rosacea?. 

 It appears, however, to be but a mere appendage of the embryo-sac, from 

 which it takes its origin, and often never reaches the base of the nucleus, and 

 therefore cannot be the medium of nutrition even to the embryo-sac. To this 

 organ, therefore, it would be better to confine the term applied to it by Du- 



