204 
POPULAR SCIENCE REVIEW. 
stamen occupies about twenty-four hours in rising up and 
discharging its pollen, and takes about the same time to 
recede, the whole period being eight days, but varying accord- 
ing to circumstances of temperature, moisture, &c.* * * § 
Berberis furnishes an instance of rapid motion ; for if the 
stamens be touched at the base of the filament, they instantly 
spring forward and strike the stigma, having previously lain 
on the surface of the spreading petals. The effects of the 
irritation on the filament of Berberis has been observed and 
described by M. E. Heckel. j* It appears that the cells of the 
irritable part are arranged in a parallel manner (the back of 
the filament being insensible). Their contents are yellow and 
disseminated throughout the cavity. After irritation, they 
undergo aggregation and contract into the centre of the cell, 
and the cell- wall is striated transversely. The cells of the back 
of the filament are contracted in repose, but extended in 
irritation. 
The stamens of the common Lucerne, Medicago sativa , as 
also of other species of that genus, suddenly curve upwards 
and remain rigidly fixed in an arched condition, having been 
previously horizontal. + 
Mr. Darwin has described numerous instances in the family 
Orchidaceae, in which the pollinia, as of the common Orchis 
mascula and others, or of Catasetum, &c., have remarkable 
powers of movement ; in the former cases slow, but in the 
latter, rapid. In every case there is discernible some special 
adaptation to the fertilization of the flowers by insect aid.§ 
Styliclium affords another illustration of rapid motion. In 
this flower the stamens and style are consolidated into a 
column, which is curiously bent and hangs over one side of 
the flower. If it be touched near the base, it instantly flies 
over to the other side. A very similar motion occurs in the 
pistil of Maranta. 
Some flowers have the stamens in a certain position on first 
expanding, but they take up another position subsequently. 
This I found to be the case with AJisma Plantago. On first 
expanding, the stamens spread out, their anthers being 
extrorse, but afterwards they curl backwards over the stigmas, 
thereby in all probability effecting self-fertilization. In 
several flowers of different species, the filaments retire after 
the anthers have shed the pollen or fallen off, as in the lemon - 
scented and oak-leafed Pelargoniums, and in Teucrium Scorodonia, 
or wood-sage. In both of these, the anthers mature some time 
* Baxter’s British Flora, vol. i. (70). 
t Bull. Soc. Bot. Fr., 1874, vol. xxi. p. 208. 
t Journ. of Linn. Soc. vol. ix. p. 827. 
§ See Fertilization of Orchids. 
