6 MEYEN ON VEGETABLE IMPREGNATION 
after this the germ-vesicle originates in the interior of the apex 
of the embryo-sac, exactly at the place where its cohesion with 
the pollen-tube occurs. The union or cohesion is here the 
act of impregnation, and the origin of the germ-vesicle the 
first product of impregnation ; the germ-vesicle is, indeed, not 
the result of a violent irruption of the pollen-tube into the 
embryo-sac, whose membrane would thereby be indented ; but 
it is formed of the substance of the two cohering membranes, 
viz. that of the end of the pollen-tube, and of the apex of the 
embryo-sac. In the figures 15, 16, 18, Plate II. this part is 
represented in a lateral view of Mesembryanthemum lingueforme 
in ddd (the end of the pollen-tube [ccc] swells here, quite 
constantly, to a very enormous size, which, however, happens 
only after effected copulation), and in fig. 17 such a position of 
the embryo-sac is represented as that the obliterated circular 
place (d) may be seen, from whence the formation of the germ- 
vesicle resulted, in the direction of the cavity of the embryo- 
sac. The germ-vesicle (e) is here already very large; it is ex- 
panded downwards, and at its extremity the substratum [ground- 
work] for the embryo is already present. During the formation 
of the germ-vesicle this circular spot (d, fig. 17) is open, as the 
substance of the two membranes there obliterated expands, in 
consequence of the act of impregnation, to form the germ- 
vesicle, which in its growth is nourished by the substance in 
the interior of the apex of the pollen-tube, as well as by the 
substance in the interior of the embryo-sac ; and from the union 
of these two substances, and their innate formative properties, 
results the new product, namely, the base for the future em- 
bryo. There is no ejaculation of the fructifying contents of the 
pollen-tube into the cavity of the embryo-sac, but the fruc- 
tifying substance passes in very slight quantity only into the 
forming germ-vesicle, soon after which this free communication 
of the originated germ-vesicle with the pollen-tube ceases by 
a constriction resulting from the formation of a diagonal sep- 
tum. Upon this, in most cases, the end of the pollen-tube 
shrivels, and very soon its former communication with the em- . 
bryo-sac ceases entirely. In other cases, however, the end of 
the pollen-tube continues for some length of time adhering to 
the embryo-sac, and then even undergoes different variations in 
form ; thus, for instance, it swells vesicularly, as in Mesembryan- 
themum lingueforme (Hort. Bot. Berol.), where this protuberance 
