230 DK. GIRAUD EMBEYOLOGY [BOOK n. 



" It has been shown," he proceeds, ' ' that the formation of 

 the embryo-sac, and the development of cytoblasts within it, 

 takes place at a period prior to the impregnation of the pistil ; 

 and that even the primary utricle itself makes its appearance 

 before the emission of the pollen from the anther, and before 

 the expansion of the stigma; so that the origin of the 

 primary utricle must not be referred to the influence of 

 impregnation, as has been already pointed out by Mirbel and 

 Spach in the case of Zea Mays. (See their paper in the 

 Annals of Natural History, v. 228.) At its first appearance 

 the primary utricle is seen to be quite distinct from the 

 embryo-sac, even at its 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 depres- 

 sion 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 fo villa, 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 

 connection, therefore, between the ovule and the columella 

 (or so-called placenta) ought not to receive the name of 



