IMPREGNATION — OVULE — SEED. 
63 
fortli from tlie nucleus, by supposing that the former, when in 
the act of enlarging itself, is forced out by the resistance of 
the already formed nucleus. The author never saw more 
than three embryos in one seed. He observes, that the cir- 
cumstance of the fructifying fluid retaining its power so long 
can scarcely be comprehended, when the long interval is con- 
sidered which intervenes between the opening of the blossom 
and the appearance of the embryo. This is observed in other 
plants ; and Ad. Brongniart is, therefore, of opinion, that the 
embryo remains for a time in a sort of torpor before it de- 
velopes itself. But, says the author, this cannot be applied to 
the mistletoe, because the ovules are not only not organized 
at the time of blossoming, but they have not even a cavity for 
the embryo. The author then makes some observations on 
impregnation in general. He says, pollen sacs exist in some 
plants ; but in others, where papillae are situated upon the 
ovule, as in the Aroideoe, they have never been observed, and 
the papillae seem to be substituted for them ; in other plants 
again, little bands (bandelettes) descend from the basis of the 
style, and are deposited in the seed near the micropyles ; for 
instance, in the Compositce, and in some others. Finally, he 
speaks of the position of the species of Viscum in the natural 
system ; the author, with Robert Brown, places them in the 
Apetalce, beside Loranthus, and next to the Santalacece ; 
Schoepfia, however, must be separated from this, and placed 
amongst the Olacinece. Three tables illustrate the researches 
of the author. 
With this we must notice Som.e further Words on the 
Act of Impregnation, and Polyemhryony in the Higher 
Plants, by F. J. F. Meyen ; Berlin, 1842, vol. ii. p. 50. The 
author first details facts, and then argues against Schleiden’s 
theory of the embryo forming itself from the pollen tube. 
The point of the embryo sac, according to his researches, com- 
bines itself with the pollen tube, and the embryo proceeds from 
this union, and, in many cases, appears as a double germinal 
vesicle. The observations related in this j)art of the treatise, 
were made upon the Mesembryanthemum pomeridianum, 
and may be considered as an epilogue to the statements made 
455 
