Page:An introduction to physiological and systematical botany (1st edition).djvu/295

 Rh these plants, and Hedwig, so famous for his discoveries among them, were both of this opinion, though the latter seems to have relinquished it. The organ in question is a membranous hood, covering the unripe fruit of these diminutive vegetables, like an extinguisher; but soon torn from its base, and elevated along with the ripening capsule. See ''Engl. Bot. t.'' 558, &c. The great peculiarity of this part, whatever it be called, consists in its summit performing the office of a stigma, as Hedwig first remarked. In Jungermannia, t. 771, &c., the very same part, differing only in usually bursting at the top to let the fruit pass, is named by Linnæus a perichætium, but very incorrectly, as we have already hinted.

Whatever office the Petals may perform with respect to air and light, it is probable that the oblong summit of the Spadix in Arum, t. 1298, answers the same purpose. When this part has been for a short time exposed to the light, it assumes a purplish brown hue, which M. Senebier seems to attribute to the same cause which he think produces the great heat observed in this flower, the