Page:An introduction to physiological and systematical botany (1st edition).djvu/279

Rh the whole scale remains, enlarges, hardens, and protects the seed, as in Pinus, the Fir tribe. Such is the case with catkins of fertile flowers, which are necessarily permanent till the seed is ripe; barren ones fall as soon as the stamens have performed their office. Every catkin consists generally of either one kind of flower or the other. There are few certain and invariable instances of stamens and pistils in the same catkin, that circumstance occurring chiefly in a few species of Salix and Carex; nor is Typha, t.  1455–7, an exception to this. Examples of barren-flowered catkins are seen, not only in Salix and Pinus, but in several plants whose fertile or fruit-bearing flowers are not catkins, such as the Walnut, and, unless I am much mistaken, the Hasel-nut, t. 723. Each nut or seed of the latter has a permanent coriaceous calyx of its own, inadvertently called by Gærtner an involucrum, though he considers the whole as an amentum, which this very calyx proves it not to be. Humulus, the Hop, t. 427, has a catkin for the fertile flower only.