884 



of the seed, and its removal before sowing would most likely prevent 

 the seed from germinating ; for it seems reasonable to conclude that 

 the two processes of the suspensor exercise the function of radicles ; 

 and at least one of these would be broken off in the act of removing 

 the carpellary coat. It is a curious circumstance that the ovulum in 

 this genus has no free funiculus, and that its coats forming the pri- 

 mine and secundine are so blended with the rest of the tissue which 

 connects the ovulum with the carpellum, that no positive line of sepa- 

 ration can be detected in that part. Indeed it is only by an attentive 

 examination of the micropyle that the existence of two coats can be 

 clearly ascertained. 



It is proper that I should notice here another somewhat mistaken 

 view entertained by Dr. Giraud, who states that there exists before 

 impregnation " a small elliptical cavity near the apex of the nucleus, 

 having a delicate lining membrane formed by the walls of the sur- 

 rounding cells : this cavity is the erabryo-sac, and a minute canal 

 may be traced leading from it to the exostome." It would be more 

 appropriate to say that the memhranous lijiing of the cavity consti- 

 tutes the embryo-sac. The cavity, however, is not confined to the 

 apex of the nucleus : its form and dimensions are represented at fig. 

 1, which exhibits a longitudinal section of the ovule and the contain- 

 ed nucleus. If the lining of this cavity be, as I suppose, the embryo- 

 sac, the contained embryo with its suspensor must have a different 

 relation to it from what has been hitherto advanced by either Schlei- 

 den or Mirbel ; for about the period of fecundation the embryo forms 

 a small elliptical body, very much smaller than the cavity in which it 

 is lodged ; it is indeed so minute as to be with great difficulty displayed 

 under the microscope. Its position and relative size are dimly seen at d, 

 fig. 1, and more clearly represented in the more highly magnified fig. 2. 

 This rudimentary embryo is described in Dr. Giraud's paper as " a 

 quantity of organizable mucilage enclosed in the embryo-sac." It is 

 true that the whole of the nuclear cavity is lined with a lax delicate 

 membrane, easily separable fi'om the nucleus itself; and that at the 

 time when the suspensor is about to perforate the coats of the ovule, 

 this membrane may be traced from the apex of the suspensor to the 

 bottom of the cavity, clearly disproving what Schleiden has asserted 

 concerning the introversion of the embryo-sac by the intrusion of a 

 pollen-tube. 



I am at a loss to understand in what mode Dr. Giraud has been 

 able to identify " the fovilla and its granules," which he records as 

 having been found abundantly in the passage leading from the style 

 to the exostome, at the time indicated by his " fourth period." If the 



