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 surrounding 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, d, 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 cell-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 
structure was so hard and resisting in my preserved specimens as not to allow of my 
examining the canal minutely; but there can be no doubt as to their 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 J). 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-saes, 
which themselves adhere to the superficial 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 efforts to the accurate observation of the ends of the 
embryo-sacs with the pollen-tubes adherent, They are tolerably easily extracted free 
from the ovary, with needles under a low doublet; I have examined at least five-and- | 
_ tions, have applied every means to make the structures clear; mounting in water and then 
in glycerine, between very thin glass, so as to observe both sides; boiling in nitric acid; 
treating with dilute sulphurie acid alone, and with this and solution of iodine; examining 
the objects with a4 and } object-glass under the compound microscope, with and without 
embryo-sac, in the situation of the ‘notch’ above mentioned (figs. 10 & 11). But I di 
incline to believe that a phænomenon analogous to conjugation takes place. For asl —— 
have said, the adhesion is intimate, but the nucleus before spoken of (Tab. XVIL 
figs. 8 & 9e) lies away from the pollen-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 de 
nucleus (figs. 10 & 11). Moreover, very soon after the pollen-tube becomes adherent, the ee 
nucleus acquires a Proper coat of cell-membrane,—becomes a real cell, 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. 119)» — 
I think that the pollen-tube, after becoming adherent to the summit of the embry0-S26, 
contents pass into the embryo-sac, reach the nucleus, and 
