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 and bursts, discharging its contents. (Fig. 12.) 
71. Physiological structure. The filament consists of a bundle 
of delicate igneous 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 dismtegrated 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 in the 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). 
‘Pa 
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 nwmber, position, relative length, connection, and 
presence. Upon these five different conditions of the stamens, 
the TWENTY-FOUR ARTIFICIAL cLassEs of Linnezeus 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 are derived from the 
Greek numerals combined with edges (57, note), as follows : — 
Class I, Monanpria (ov0s, solitary,) includes all genera (52) 
of plants with one stamen to each flower. 
