Page:An introduction to physiological and systematical botany (1st edition).djvu/302

 268 [sic] with a crest, as in many Ericæ, and the genus Pinus. See Mr. Lambert's splendid work.

The Pollen, or Dust, is contained in the Anther, from which it is thrown out chiefly in warm dry weather, when the coat of the latter contracts and bursts. The Pollen, though to the naked eye a fine powder, and light enough to be wafted along by the air, is so curiously formed, and so various in different plants, as to be an interesting and popular object for the microscope. Each grain of it is commonly a membranous bag, round or angular, rough or smooth, which remains entire till it meets with any moisture, being contrary in this respect to the nature of the Anther; then it burst with great force, discharging a subtile vapour. In the Orchis family, and some other plants, the pollen is of a glutinous nature, very different from its usual aspect. See remarks on Mirabilis longiflora, ''Exot. Bot. v.'' 1. 44.

The stamens are changed to petals in double flowers, and rendered useless. They are often obliterated by excessive