72 PROFESSOR HENFREY ON THE DEVELOPMENT OF THE OVULE 



mity (Tab. XVII. figs. 8 & 9, e). A portion of the protoplasm in the absolute extremity 

 (adherent to the placenta) collects into two granular masses, which become much darker- 

 coloured than the sm-roundiug substance, and apparently almost solid, while the closed 

 end of the embryo-sac becomes moulded as it were on these so as to present a kind of 

 notch or depression between them (figs. 8 & 9, rf, d). They lie nearly in contact, occupying 

 (like a plug) the summit of the embryo-sac ; the nucleus before mentioned being quite 

 below them. At this period the nucleus is devoid of a ceU-membrane. 



The summits of embryo-sacs, examined soon after the above period, present the ends of 

 one or more tubes adherent to them ; these tubes extend down to the embryo- sacs from 

 the summit of the placental column; I have never traced them up the style, for this 

 structiu-e was so hard and resisting in my preserved specimens as not to aUow of my 

 examining the canal minutely ; but there can be no doubt as to theu' nature. They are 

 the ends of pollen-tubes. Usually one applies itself upon the very apex of the embryo- 

 sac (Tab. XVII. figs. 10 & 11/). The tubes appear to creep down between the papillose 

 projections of the cells of the surface of the placenta, being moulded in some degree on 

 them ; and these grooves appear to conduct the tubes to the points of the embryo-sacs, 

 which themselves adhere to the su2:)erficial cells of the placenta ; sometimes so firmly as 

 to carry away fragments of their walls when dissected out free (Tab. XVII. figs. 9-11). 



I have directed my utmost eff'orts to the accurate observation of the ends of the 

 embryo-sacs with the pollen-tubes adherent. They are tolerably easDy extracted free 

 from the ovary, with needles under a low doublet ; I have examined at least five-and- 

 twenty at various times during the last year and a half, and in the course of the observa- 

 tions, have applied every means to make the structures clear ; mounting iri water and then 

 in glycerine, between very thin glass, so as to observe both sides ; boiling in nitric acid ; 

 treating with dilute sulphiu'ic acid alone, and with this and solution of iodine ; examining 

 the objects with a \ and \ object-glass under the compound microscope, with and without 

 the condenser for illumination, by direct and oblique light. 



The end of the poUen-tube adheres so fiirmly to the end of the embryo-sac, that it cannot 

 lie torn away in a really fertilized ovule. 



My decided opinion is that Griffith was in error in stating that the pollen penetrates 

 into the embryo-sac ; I believe that it only applies itself firmly against it, over the point 

 where the line of division exists between the two coagula lying on the apex of the 

 embryo-sac, in the situation of the 'notch' above mentioned (figs. 10 & 11). But I 

 incline to believe that a phajnomenon analogous to conjugation takes place. For, as I 

 have said, the adhesion is intimate, but the nucleus before spoken of (Tab. XVII. 

 figs. 8 & 9 e) lies away from the poUen-tube, separated from it by the two coagula {d, d) ; 

 the fissure, however, between these leads exactly from the end of the pollen-tube to the 

 nucleus (figs. 10 & 11). Moreover, very soon after the pollen- tube becomes adherent, the 

 nucleus acquires a proper coat of ceU-membrane, — becomes a real ceU, the germinal 

 vesicle, from which the suspensor is developed. This cell is slightly pyriform, with an 

 obtuse projection directed toward the fissure between the coagula (Tab. XVII. fig. 11 g). 



I think that the pollen-tube, after becoming adherent to the summit of the embryo-sac, 

 bursts into it, and that the contents pass into the embryo-sac, reach the nucleus, and 



