36 THE FLOWER. 



usually spherical, but in some plants cubical, in others triangu 

 lar, in others still, polygonal, &c., always being of the same form 

 in the same species. (Fig. 7.) 



a. Each grain of pollen has been ascertained to consist of a membranous sack 

 containing a fluid. In this fluid are suspended molecules of inconceivable 

 minuteness, possessed of a tremulous motion. When the membrane is exposed 

 to moisture, it swells arid bursts, discharging its contents. (Fig. 12.) 



71. Physiological structure. The filament consists of a bundle 

 of delicate ligneous tissue, with spiral vessels, surrounded by 

 cellular tissue, the same tissues which compose the stem of the 

 leaf (260). The same tissues have also been traced into the 

 connectile. The anther consists almost wholly of cellular tissue, 

 corresponding to the fleshy substance (parenchyma) of the leaf. 

 The pollen consists of disintegrated bladders of the same tissue. 



72. Theoretical structure. Thus it is evident, as we have already seen, that 

 however much the stamen may differ in aspect from a leaf, they both have the 

 same original plan. This is further evident, from the gradual transition of sta- 

 mens into petals, as seen injhe water-lily or the double rose. In the former, the 

 process is so gradual that the outer whorls exactly resemble petals, except in having 

 the tops developed into yellow anthers, while in the rose we find organs in every 

 conceivable state of transition from stamens to petals. That the petals are modi- 

 fied leaves, will hereafter be more definitely shown (106). 



FIG. 8. Stamens of the water-lily gradually passing into petals. 



73. The stamens vary in the different kinds of plants, in re- 

 spect to their number, position, relative length, connection, and 

 presence. Upon these five different conditions of the stamens, 

 the TWENTY-FOUR ARTIFICIAL CLASSES of Linna3us are founded. 



74. 1st Number. The first eleven classes are founded upon 

 the number of the stamens the stamens being also free (63, 

 c.), and of equal length. Their names arc derived from the 

 Greek numerals combined with avdyeg (57, note), as follows : 



Class I, MONANDRIA (povog, solitary,) includes all genera (52) 

 of plants with one stamen to each flower. 



