1846.] Fertilization of Plants. 55 



In the nettle tribe, laiicacecE, when the flower first expands, 

 the filament is rolled inwards and the anther is near the centre 

 and base of the flower, when all is perfected, the filament sudden- 

 ly straightens itself, and the anther opens and a cloud of pollen 

 is diffused in the air, to light upon the stigmas in the neighbor- 

 hood. After the disengagement of the pollen, the stamen, as 

 though exhausted by the effort, lies down flat in the bottom of 

 the calyx. 



In the recently expanded flower of the rue, ruta graveoleus, 

 we observe eight or ten stamens lying horizontally in the bottom 

 of the flower. Each stamen, one by one, and in an unvarying 

 order, raises itself, and brings its anther against the stigma, dis- 

 engaging at the same time its store of pollen. After it has thus 

 paid its tribute, the stamen slowly returns to its former position, 

 and soon withers away, having accomplished the end of its crea- 

 tion. Prof. Wydlei", of Berne, has published a memoir on the 

 physiological condition of this regular and curious arrangement of 

 the rue. 



Our kalmia affords an interesting object of observation in this 

 respect. When the flower expands, the anthers find themselves 

 engaged each in a little cavity in the bottom of the corolla. To 

 extricate themselves w^ould seem impossible, but the filament 

 curves up, as we should curve up our arm if our hand was lying 

 on a flat surface, and we wished to bring it nearer to us, and thus 

 draws the anther from its confinement and raises it to the stigma. 

 The above are the common and some of the particular modes 

 adopted by nature to bring the pollen to the stigma. 



The stigma is usually the summit of the style. It is a glutin- 

 ous, moist surface, consisting of naked, spherical cells, there being 

 no epidermis over this portion of the plant. When the pollen 

 grains fall upon this surface, they are retained by the viscidity, 

 and the moisture affords the means of producing the pollen tubes. 

 These when emitted, which is usually from the under surface of 

 the grain, penetrate the loose cellular tissue of the central portion 

 of the style, and enter the cavity of the ovarium and the foramen 

 of the ovule. 



