Brown^s Microscopical Observations. 47 



the month of June, 1827, he examined the grains of pollen 

 belonging to the Clarkia pulchella, a plant just then brought 

 from the north-west coast of America, by Mr. David Douglas, 

 which grains, taken from the anthers full grown, but before 

 bursting, were filled with particles, or granules, of unusually 

 large size, varying from 4 oVo to 3^^077 of an inch in length, and 

 of a figure between cylindrical and oblong, perhaps slightly 

 flattened, and having rounded and equal extremities. While 

 examining these particles immersed in water, he observed 

 many of them very evidently in motion ; their motion consist- 

 ing, not only of a change of place in the fluid, manifested by 

 alterations in their relative positions, but also not unfrequently 

 of a change of form" in the particle itself; a contraction or 

 curvature taking place repeatedly about the middle of one 

 side, accompanied by a corresponding swelling or convexity 

 on the opposite side of the particle. In a few instances the 

 particle was seen to move on its longer axis. These motions 

 were such as to satisfy him, that they arose neither from 

 currents in the fluid, nor from its gradual evaporation, but 

 belonged to the particle itself. 



He extended his observations to many other plants belong- 

 ing to the same natural family, namely Onagrarige, and found 

 the same general form and similar motions of particles : and, 

 indeed, in all the different families he examined, particles were 

 found varying in form from oblong to spherical, having mani- 

 fest motions similar to those already described. In the grasses 

 the membrane of the grain of pollen is so transparent, in some 

 cases, that the motion of the particles within the entire grain 

 was distinctly visible, and it was manifest also in some other 

 plants. This is the first stage of his observations. 



The second and most curious stage is, that in looking after 

 these particles he saw others of a much smaller size, of a dif- 

 ferent shape, apparently spherical, and in rapid oscillating 

 motion. These he denominates Molecules. He found them 

 in the anthers of mosses, and on the surface of the bodies 

 regarded as the stamina of JE^quisetum (Horsetail), and then in 

 bruised portions of other parts of the same plants. He now 

 thought he had got hold of the constituent or elementary 

 molecules of organic bodies, first so considered by Buffbn and 

 Needham, then by Wrisburg with greater precision, soon 

 after and still more particularly by Miiller, and very recently 

 by Dr. Milne Edwards. Following up this examination of 

 organic bodies, he found the molecules to exist in various 

 animal and vegetable tissues, whether living or dead ; in 

 gum resins, and substances of vegetable origin, such as pit- 

 coal, and other mineralised vegetable remains. He then went 



