5$1?0 Mr Brown an the Eouistence of Active Molecules 



Before I engaged in the inquiry in 1827, I was acquainted only 

 with the abstract given by M. Adolphe Brongniart himself, of 

 a very elaborate and valuable memoir, entitled " Recherches 

 sur la Generation et le Developpement de VEmhryon dans les 

 Vegetaux Phanerogames^'' which he had then read before the 

 Academy of Sciences of Paris, and has since published in the 

 Annates des Sciences Naturelks. 



Neither in the abstract referred to, nor in the body of the 

 memoir, which M. Brongniart has, with great candour, given in 

 its original state, are there any observations, appearing of im- 

 portance even to the author himself, on the motion or form of 

 the particles ; and the attempt to tracei these particles to the 

 ovulum with so imperfect a knowledge of their distinguishing 

 characters, could hardly be expected to prove satisfactory. Late 

 in the autumn of 1827, however, M. Brongniart having at his 

 command a microscope constructed by Amici, the celebrated Pro- 

 fessor of Modena, he was enabled to ascertain many important 

 facts on both these points, the result of which he has given in 

 the notes annexed to his memoir. On the general accuracy of 

 his observations on the motions, form, and size of the granules, 

 as be terms the particles, I place great reliance. But, in at- 

 tempting to trace these particles through their whole course, he 

 has overlooked two points of the greatest importance in the in- 

 vestigation. 



For, in the first place, he was evidently unacquainted with 

 the fact, that the active spherical molecules generally exist in 

 the grain of pollen along with its proper particles ; nor does it 

 appear from any part of his memoir that he was aware of the 

 existence of molecules having spontaneous or inherent motion, 

 and distinct from the peculiar particles of the pollen, though he 

 has doubtless seen them, and in some cases, as it seems to me, 

 described them as those particles. 



Secondly, He has been satisfied with the external appearance 

 of the parts in coming to his conclusion, that no particles capa^ 

 ble of motion exist in the style or stigma before impregnation. 



That both simple molecules and larger particles of different 

 form, and equally capable of motion, do exist in these parts, be- 

 fore the application of the pollen to the stigma can possibly take 

 place, in many of the plants submitted by him to examination, 

 may easily be ascertained; particularly in Antirrhinum majttSy 



