44 THIRD REPORT — 1833. 



The Origin of the Pollen, connected as it intimately is with 

 the singular pha;nomena of vegetable sexuality, has naturally 

 been of late an object of some inquiry. To the important dis- 

 coveries of the younger Brongniart and of Dr. Robert Brown, 

 M. Mirbellias added some observations*, detailed with that 

 admirable clearness and precision which give so great a value 

 to all his writings, and which are the more interesting as they 

 serve to explain what was before obscure, and to correct what 

 appears to have been either inaccurately or imperfectly de- 

 cribed. This he has been enabled to do by beginning his in- 

 quiry at the very earliest period when the organization of the 

 anther can be discovered: bis subject was the common Gourd. 

 At a very early time the whole tissue of the anther is of the 

 most perfect uniformity, consisting of cellules, the transverse 

 section of which represents nearly regular hexagons and penta- 

 gons. In every cell, without even excepting those which com- 

 pose the superficies of the anther, are found little loose bodies, 

 so exceedingly minute that a magnifying power of 500 or 600 

 diameters is scarcely sufficient to examine them: they may be 

 compared to transparent, neai'ly colourless vesicles, more or 

 less round, and of unequal size. At a stage but little more ad- 

 vanced, you may observe on each side of the medial line of a 

 transverse section of a lobe of an anther, a collection of cellules 

 rather larger than the remainder: it will afterwards be seen 

 that it is here that tlie pollen is engendered; such cells are 

 therefore called pollen-cells. In a bud, a line and a half or two 

 lines in diameter, some remarkable alterations were found to 

 have taken place ; the pollen-cells had enlarged and their gra- 

 nules had so much increased in number, that they nearly filled 

 the cells in opake masses. These granules and pollen-cells 

 formed together a greyish mass, connected with the rest of the 

 tissue by the intervention of a cellular membrane, which, not- 

 withstanding its organic continuity with the suri'ounding parts, 

 is at once distinguishable ; for while the cells of the surrounding 

 parts elongate parallel to the plane of the surface, and to the 

 plane of the base of the anther, those of the cellular membrane 

 elongate from the centi'e to the circumference. In more ad- 

 vanced anthers, the sides of the pollen-cells, from being thin 

 and dry, had changed to a perceptible thickness, and their sub- 

 stance, gorged with fluid, resembled a colourless jelly. When 

 the buds were three or four lines long, an unexpected phaeno- 

 menon presented itself. At first the thick and succulent walls 

 of each pollen-cell dilated so as to leave an empty space between 

 the inner face and the granules, not one of which sepiu'ated 

 * "Complement des Observations," S{f., as above quoted. 



