360 Mr Brown wi t?ie Existence of Active Molecules 



as to satisfy me, after frequently repeated observation, that they 

 arose neither from currents in the fluid, nor from its gradual 

 evaporation, but belonged to the particle itself. 



Grains of pollen of the same plant taken from antherae imme- 

 diately after bursting, contained similar subcylindrical particles, 

 in reduced numbers, however, and mixed with other particles, 

 at least as numerous, of much smaller size, apparently spherical, 

 and in rapid oscillatory motion. 



These smaller particles, or molecules, as I shall term them, 

 when first seen, I considered to be some of the cylindrical par- 

 ticles swimming vertically in the fluid. But frequent and care- 

 ful examination lessened ray confidence in this supposition ; 

 and on continuing to observe them until the water had entirely 

 evaporated, both the cylindrical particles and spherical mole- 

 cules were found on the stage of the microscope. 



In extending my observations to many other plants of the 

 same natural family, namely Onagrariaej the same general form 

 and similar motions of particles were ascertained to exist, espe- 

 cially in the various species of CEnothera, which I examined. 

 I found also in their grains of pollen taken from the antherae 

 immediately after bursting, a manifest reduction in the propor-. 

 tion of the cylindrical or oblong particles, and a corresponding 

 increase in that of the molecules, in a less remarkable degree, 

 however, than in Clarckia. 



This appearance, or rather the great increase in the number 

 of the molecules, and the reduction in that of the cylindrical 

 particles, before the grain of pollen could possibly have come in 

 contact with the stigma, — were perplexing circumstances in this 

 stage of the inquiry, and certainly not favourable to the suppo- 

 sition of the cylindrical particles acting directly on the ovulum ; 

 an opinion which I was inclined to adopt, when I first saw them 

 in motion. These circumstances, however, induced me to muL 

 tiply my observations, and I accordingly examined numerous 

 species of many of the more important and remarkable families 

 of the two great primary divisions of phaenogamous plants. 



In all these plants particles were found, which in the diff*erent 

 families or genera varied in form from oblong to spherical, ha- 

 ving manifest motions similar to those already described ; ex- 

 cept that the change of form in the oval and oblong particles was 



