Page:Popular Science Monthly Volume 20.djvu/802

780 supposing the complete exclusion of the two others." The reign of Acrogens was manifest during the Carboniferous and Permian periods; the reign of the Gymnosperms during the Vosgian and Jurassic; and the reign of the Angiosperms during the Cretaceous and Tertiary periods.

Proceeding to the study of the fossil seeds found silicified in the coal-beds of Saint-Étienne, M. Brongniart makes a comparative review

 (magnified three times). a, albumen, well preserved, inclosed in the embryonary sac; b, hardly visible remains of the embryonary sac; c, envelope of the kernel reduced to its epidermis; co, the two corpuscles, placed symmetrically in the plane of the seed, below the pollinical chamber; m, the pollinical chamber, but slightly developed in this group of seeds; d, endotesta; mi, micropylary canal of the testa, leading to the pollinical chamber; ch, chalazian region of the seed.

of the structure of the seed and ovule of the cycads, and of different silicified seeds of the coal-beds, and announces one of the most remarkable discoveries in fossil botany, the value of which consists in the light which the study of fossils is made to cast upon the interior anatomy of existing forms. A singular feature was observed in the organization of a considerable number of these seeds, in that there existed, near the summit of the kernel, and in the corresponding part of the micropyle of the testa (or outer integument), a cavity in the cellular tissue, containing nearly always granules or free vesicles, which could only be regarded as grains of pollen; and from the presence of which M. Brongniart was led to designate the cavity as the pollinical chamber. Nothing of the kind is known in existing gymnosperms. The cycads, however, had been previously indicated as presenting analogies with the Palæozoic plants under study; and M. Brongniart's views upon this point have received a striking confirmation from the observations of the gardener of the museum and of M. Renault. The published volume of the "Lectures on Fossil Botany" of the latter gentleman contains a carefully copied plate, showing a similar pollinical chamber in the Ceratozamia Mexicana. Figs. 2 and 3 show the grains very plainly in Cardlo carpus sclerotesta.