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- 

 ger 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. 



The smaller particles, or molecules as they are termed by Brown, 

 were first observed by tliis distinguished naturalist in the pollen of 

 ClarJcia pulchella, mingled with the larger granules already descri- 

 bed ; and they have since been detected in a great number of species. 

 They 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, m.oreover, that their 

 motions were equally vivid, whether taken from the living plants or 



* An account of microscopical observations made in tke months of June, Jul'if, 

 and August, 1827, u,fon the particles contained in the pollen of plants, and upon 

 the general existence of active moleciiles in organized and inorganized bodies ; by 

 R. Brown. I re-lranslate from a French translation, published in the Annales 

 des Sciences Naturelles, Vol. 14, p. 341 ; not having been able to procure the ori- 

 ginal pamphlet, which was only printed for distribution among the friends of th^ 

 author, and is now very scarce. 



Vol. XXXL— No. 2. 40 



