ON ACTIVE MOLECULES. 479 



parts, before the application of the pollen to the stigma can 

 possibly take place, in many of tlie plants submitted ])yhim 

 to examination, may easily be asceitained ; particularly in 

 Antirrhinum majus, of which he has given a ligure in a 

 more advanced state, representing these molecules or parti- 

 cles, Avhicli he su])poses to have been derived from the 

 grains of pollen, adhering to the stigma. 



There [ire some other ])oints respecting the grains of 

 pollen and their contained particles in which I also differ 

 from M. Brongniart, namely, in his supposition that the 

 particles are not formed in the grain itself, but in the cavity 

 of the anthera ; in his assertion respecting the ])resence of 

 pores on the surface of the grain in its early state, through 

 wdiich the ])artieles formed in the anthera pass into its 

 cavity ; and lastly, on the existence of a membrane forming 

 the coat of his boyan or mass of cylindrical form ejected 

 from the grain of pollen. 



I reserve, however, my observations on these and several 

 other topics connected with the subject of the present in- 

 quiry for the more detailed account, which it is my intention 

 to give. 



July 30M, 1828. 



ADDITIONAL REMARKS ON ACTIVE 

 MOLECULES. 



By ROBERT BROWN, F.R.S. 



About twelve months ago I printed an account of Mi- 

 croscopical Observations made in the summer of 1S27, on 

 the Particles contained in the Pollen of Plants ; and on the 

 general Existence of active Molecules in Organic and In- 

 organic Bodies. 



