He divided plants into sexual and asexual, the former being Phanerogamous or flowering, and the latter Cryptogamous or flowerless.
The whole subject of fertilization and development of the embryo has been more recently investigated with great assiduity and zeal, as regards both cryptogamous and phanerogamous plants, and details must be sought in the various special articles.
The number of different species is estimated at 12,000, of which one-third are phanerogamous,or flowering plants, and two-thirds cryptogamous, or flowerless.