68 SCIENCE PRIMERS. [xvn. 



the others, which others may all overlap by one margin, 

 or one of them may be inside all the others (petals of 

 apple). 2. Twisted, when each overlaps by one 

 margin the contiguous margin of that next to it 

 (corolla of periwinkle, convolvulus). 3. Valvate, 

 when they meet by their edges without overlapping 

 (calyx of mallow). 4. Open, when they grow quite 

 apart, neither overlapping nor touching (petals of 

 mignonette). 



FIG. 46. ^Estivations : a, imbricate ; t>, twisted ; c, valvate, with the edges 

 turned outward. 



102. The stamens usually grow straight from the 

 first, but are sometimes curved or rolled inwards 

 (myrtle and nettle), or backwards (kalmia). 



XVII. THE STAMEN. 

 ANTHER, POLLEN, FILAMENT. 



103. The stamen consists essentially of the anther, 

 a 2-lobed, 2-celled organ filled with granules (the 

 pollen); its lobes are placed right and left to the 

 axis of the flower. The anther may or may not 

 have a stalk (filament), which contains a vascular 

 bundle (Par. 9) that terminates between the anther- 

 lobes. The use of the stamen is to form, contain, and 

 discharge the pollen. 



