64 PEOCEEDINGS OF THE 



motion of all sufficiently minute particles if suspended in fluid, 

 which has received the name of the Brovvnian or Brunonian 

 motion. 



It remains to be seen which of the motions Brown saw were 

 physical (i. e. Browniaii) or biological {i. e. protoplasmic) ; for 

 it is to be remembered that at the time he made his observations 

 he could have known nothing of the movements of protoplasm, to 

 which the motions of the large particles within the pollen-grain may 

 be ftttributable. 



At the conclusion of his Additional Eemarks, he gives an 

 interesting account of the observations on the movements of 

 particles in organic substances made by previous observers, 

 amongst whom he mentions Gleichen as the discoverer of 

 motions in the particles contained within the pollen and in the 

 ovulum of Zea Mays. In another place he alludes to the obser- 

 vations of Brongniart on the same subject, contained in that 

 author's " Eecherches sur la generation et le developpement de 

 I'embryon dans les Vegetaux Phanerogames," observing that 

 he was evidently unacquainted with the fact that the active 

 spherical molecules generally exist in the grains of pollen along 

 with its proper particles. 



I have ventured to dwell at length upon this memoir of 

 Brown's, because it is in many respects the most remarkable as 

 an investigation, because I think that his observations and experi- 

 ments have not been repeated as perhaps they deserve to be, 

 because I find that very few of the younger generation of 

 botanists are carefully acquainted with the singular history of 

 the Brownian motion. 



As before stated, Brown, in 1831, read before this Society his 

 observations on the fecundation of Orcliidece and Asdepiadecd ; 

 and, in 1832, his " Additional Observations " on the same subject, 

 along with which may be noticed the " Supplementary Observa- 

 tions," which were intended to be a reprint from a separate pub- 

 lication, but which were reserved for private distribution, and I 

 believe never published. 



The sum of these memoirs represents what is unquestionably 

 the masterpiece of Brown's many works, and includes his most 

 valuable contributions to botanical science. The investigation 

 is alike remarkable for the difficulty of the subject, the amount 

 of labour expended upon it, the multitude of details mastered, 

 its completeness as far as the author could carry it, and its far- 

 reaching results. Commencing with the OrcJiidece, tlie labours 

 of all who have investigated their reproductive organs and their 

 functions, from Haller in 1760 to Lindley in 1830, are recorded, 

 to be followed by his own far more accurate, profound, and com- 

 plete analyses. In the course of these investigations he detects 

 the " areola or nucleus " of the vegetable cell, which, indeed, had 

 been seen by a few previous observers, who had not, however, 

 recognized its importance. This Brown did, and it led him to 



