Remarks on the Impregnation of Plants. 313 
revolve upon its longer axis. I was convinced, from repeated ob- 
servations of these movements, that they are produced neither by 
currents in the fluid nor by gradual evaporation, but that they per- 
tain to the particles themselves.”’** The same phenomena were ob- 
served both by Brown and Brongniart, in a great number of plants 
of different families, with the exception that the change of form in 
the particles themselves was less evident when these are oval or 
oblong in shape, and perhaps never apparent when they are spher- 
ical. It is worthy of remark, moreover, that Ad. Brongniart obser- 
ved that the somewhat cylindrical granules of the pollen of several 
Malvaceous plants repeatedly exhibited a double curvature like the 
letter S. The movements of the larger granules are never rapid, 
and are frequently very slow. ‘The same motions were observed in 
the granules of pollen taken from recently dried specimens, and also 
from those that had been kept for several days and even for some 
months in weak alcohol; but in pollen taken from dried specimens 
which had been preserved, some twenty, and others more than one 
hundred years, Dr. Brown found that, although the movements of 
the molecules or smaller particles were unaffected, those of the lar- 
Ser granules were scarcely evident, and often not at all apparent. 
According to Brongniart’s observations, the movements of granules 
from fresh pollen were suddenly checked when put into alcohol. 
a smaller particles, or molecules as they are termed by Brown, 
re first observed by this distinguished naturalist in the pollen of 
Clarkia pulchella, mingled with the larger granules already 
bed; and they have since been detected in a great number of species. 
ey differ from the larger granules not only by their size, which va- 
ries from the 15,000th to the 30,000th of an inch in diameter, but 
also in their form, which is always spherical, and in their movements, 
which are oscillatory and extremely rapid. ‘These molecules were 
also observed in the powder of the so-called anthers of mosses and 
other flowerless plants by Brown, who found, moreover, that their 
motions were equally vivid, whether taken from the living plants or 
* An account of microscopical observations made in the months of June, July, 
the general existence of active molecules in organized and inorganized bodies ; by 
R. Brown. I re-translate from a French peucnie published in the Annales 
des Sciences Naturelles, Vol. 14, p.341; not having been able to procure the ori- 
ginal pamphlet, which was Hen printed for distribution among the friends of the 
author, and is now ve 
Vou. XXXL—No. : 2. 40 
