06^ Mr Brown on the Existence of Active Molecules 



determinate point of its surface with the stigma or glandular 

 process of that organ. 



Having found motion in the particles of the pollen of all the 

 living plants which I had examined, I was led next to inquire 

 whether this property continued after the death of the plant, 

 and for what length of time it was retained. 



In plants, either dried or immersed in spirit for a few days 

 only, the particles of pollen of both kinds were found in motion 

 equally evident with that observed in the living plant ; speci- 

 mens of several plants, some of which had been dried and pre- 

 served in an herbarium for upwards of twenty years, and 

 others not less than a century, still exhibited the molecules or 

 smaller spherical particles in considerable numbers, and in evi- 

 dent motion, along with a few of the larger particles, whose 

 motions were much less manifest, and in some cases not observ- 

 able *. 



In this stage of the investigation, having found, as I be- 

 lieved, a peculiar character in the motions of the particles of 

 pollen in water, it occurred to me to appeal to this peculiarity 

 as a test in certain families of Cryptogamous plants, namely. 

 Mosses, and the genus Equisetum, in which the existence of 

 sexual organs had not been universally admitted. 



In the supposed stamina of both these families, namely, in 

 the cylindrical antherae or pollen of Mosses, and on the surface 

 of the four spathulate bodies surrounding the naked ovulum, as 

 it may be considered, of Equisetum, I found minute spherical 

 particles, apparently of the same size with the molecule de- 

 scribed in Onagrariae, and having equally vivid motion on im- 

 mersion in water ; and this motion was still observable in speci- 

 mens both of Mosses and of Equiseta, which had been dried 

 upwards of one hundred years. 



• While this sheet was passing through the press, I have examined the 

 pollen of several flowers which have been immersed in weak spirit about ele- 

 ven months, particularly of Viola tricolor^ Zizania aquatka^ and Zea Mays ; 

 and in all these plants the peculiar particles of the pollen, which are oval or 

 short oblong, though somewhat reduced in number, retain their form perfect- 

 ly, and exhibit evident motion, though, I think, not so vivid as in those be- 

 longing to the living plant. In Viola tricolor^ in which, as well as in other 

 species of the same natural section of the genus, the pollen has a very re- 

 markable form, the grain on immersion in nitric acid still discharged its con- 

 tents by its four angles, though with less force than in the recent plant. 



