Impregnation of Plants. 143 



doubted, the correctness of their observations has lately been abundantly 

 confirmed by the admirable researches of Ad. Brongniart and Mirbel. An 

 account of some recent observations by the last named author is append- 

 ed to his incomparable memoir on Marchantia, where he has also giv- 

 en a representation of the two coats. 



" A magnifying power of two or three hundred diameters reveals 

 the existence of two kinds of granules in the fluid of the pollen- 

 grain. The larger kind, which are also the fewer in number, have 

 been particularly examined by Ad. Brongniart and Brown, whose 

 researches, made about the same time, and wholly independently of 

 each other, coincide in almost every particular.* These granules 

 are peculiar to pollen, and have been detected in every plant that 

 has been submitted to examination. They differ in shape in differ- 

 ent plants, but are uniform in the same species. The following is 

 extracted from the account of these granules, given by R. Brow n, as 

 they appeared in the pollen of the plant which he first submitted to ex- 

 amination. ' This plant was Clarkia pulchella, in which the pollen-grains 

 taken from the anthers when completely developed, but before their de- 

 hiscence, were filled with particles or granules of a size varying from 

 the 4000th to about the 5000th of an inch in length, their form being in- 

 termediate between cylindrical and oblong, slightly flattened perhaps, 

 the extremites being rounded and equal. While examining the form 

 of these particles floating in a drop of water, I observed that many of 

 them were evidently in motion. Their movements were not confined to 

 a mere change of place in the fluid, as manifested by modifications in 

 their relative position, but there was frequently a change of form in the 

 particle itself; and several times a conti-action or incurvation was per- 

 ceived near the middle of a particle on one side, accompanied by a cor- 

 responding convexity on the opposite side. In some instances the par- 

 ticle was seen to revolve upon its longer axis. I was convinced, from 

 repeated observations of these movements, that they are produced nei- 

 ther by currents in the fluid nor by gradual evaporation, but that they 

 pertain to the particles themselves. 'f The same phenomena were 

 observed both by Brown and Brongniart, in a great number of 

 plants of different families, with the exception that the change of 

 form in the particles themselves was less evident when these are 

 oval or oblong in shape, and perhaps never apparent when they are 

 spherical. It is worthy of remark, moreover, that Ad. Brongniart observ- 

 ed that the somewhat cylindrical granules of the pollen of several Mal- 

 vaceous plants repeatedly exhibited a double curvature like the letter S. 

 The movements of the larger granules are never ra])id, and are 

 frequently very slow. The same motions were observed in the granules 

 of pollen taken from recently dried specimens, and also from those that 

 had been kept for several days and even for some months in weak alco- 

 hol; but in pollen taken from dried specimens which had been preserved 

 some twenty, and others more than one hundred years, Dr. Brown 

 found that, although the movements of the molecules or smaller particles 



* " Tlipse grannies were discovered and described by Needham as long ago as the 

 year 1750. He even svgse.sts that they penetrate to the ovule and form the embryo. 

 This is not the only instance in wiiich llic observations and suggestions of this 

 authof, after having deen donbted or left in obsnnrily for nearly seventy years, have been 

 recently confirmed, or rendered extremely probable." 



t "An accov.nt of microscopical observations made in the months of June, July, and Au- 

 gust, 1827, upon the particles contained in the pollen of plants, and upon the general exist- 

 ence of active molecules in organized and inorganized bodies; by K. Brown. I re-translate 

 from a French translation, published in the Annales des Sciences ^■aturelles, Vol. 14, p. 

 341 ; not having been able to procure the original pamphlet, which was only printed for 

 distribution among the friends of llie author, and is uo^v very scarce." 



