1211. The known number of species in the vegetable kingdom has been gradually enlarged by the progress of maritime and inland discovery; but owing to great districts of the globe not having yet been explored by the botanist, the interior of Africa, and Australia, with sections of America, Asia, and Oceanica, it is impossible to state the exact amount. The successive augmentation of the catalogue appears from the numbers below: Species. Theophrastus 500 Pliny 1,000 Greek, Roman, and Arabian botanists 1,400 Bauhin 6,000 Linnæus 8,800 Persoon 27,000 Humboldt and Brown 38,000 De Candolle 56,000 Lindley 86,000 Hinds 89,000 1212. Vegetable forms are divided into three great classes which differ materially in their structure:--1. Cryptogamous plants--those which have no flowers, properly so called, mosses, lichens, fungi, and ferns: as distinguished from those which are phænogamous, or flower-bearing, to which the two following classes belong. 2. Endogenous plants, which have stems increasing from within, also called Monocotyledons, from having only one seed-lobe, as the numerous grasses, lilies, and the palm family. 3. Exogenous plants, which have stems growing by additions from without, also called Dicoteledons, from the seed consisting of two lobes, the most perfect, beautiful, and numerous class, embracing the forest trees, and most flowering shrubs and herbs.