IMPREGNATION — OVULE — SEED. 
65 
Remarks on the Impregnation of Plants are also found in 
the Journal de Pharmazie, 1840, p. 751, by M. Fromond ; see 
also Flora, 1841, p. 204. He particularly treats of the cases 
where the stigma is situated above the anthers. The author 
is of opinion, that wind or insects are not always required to 
facilitate the impregnation ; indeed, he does not even consider 
it philosophical to have recourse to these modes of explana- 
tion in such cases. Impregnation, according to the author, 
only takes place some time after the opening of the flower, 
and when the corolla twists itself on the approach of the 
period of ’withering. This is the case in Iris, The pollen 
here precipitates itself upon the basis of the style on the 
bursting of the anther; the parts of the flower afterwards 
become erect, and bend themselves towards the centre of the 
flower, and thus the pollen is sprinkled upon the stigma. The 
same process also takes place in Sisyrinchium and Morcea. 
The flower in Ipomoea and Convolvulus is twisted into a spiral 
form after the bursting of the anther, and completely encloses 
the style ; the corolla is afterwards loosened at the base, and 
glides down on the style by the slightest motion of the air, 
and the pollen situated upon it thus comes into contact with 
the stigma. The anthers in the Malvaceae strew the pollen 
about far and near in the morning, so that it is partially pre- 
cipitated upon the petals, which latter are brought towards 
the centre of the flower in the evening, thus enabling the pollen 
lying upon them to come into contact with the stigma. Many 
flowers are twisted in a spiral form, so as perfectly to enclose 
the stigmas. 
M. Treviranus made Remarks on the Hairs on the Style 
of the Species of Campanula (see Flora, 1840, p. 680), to the 
Assembly of Naturalists at Erlangen. He agrees with Ad. 
Brogniart in the opinion, that impregnation in these plants is 
elfected in the usual way, by pollen tubes, which he found upon 
the stigma. Brogniart found that these hairs did not fall off, 
but drew back into a sheath, like the claws of a beast of prey ; 
which Treviranus confirms. The latter found pollen-globules 
within the cavity of the hair itself ; they therefore cannot 
have come into the hair accidentally, as Brogniart believes. 
467 
