374 ILLUSTRATIONS OF THE NATURAL OHDKUS. 



lowest grade of Flowerless plants. The first mode possesses the 

 theoretical advantage of ascending by successive steps from the 

 simplest to the most complex structure ; the second, the great prac- 

 tical advantage of beginning with the most complete and best under- 

 stood, and proceeding gradually to the most reduced and least 

 known forms, or, in other words, from the easiest to the most dif- 

 ficult ; and is therefore the best plan for the student. 



735. Until the orders shall have been successfully associated into 

 natural alliances or superior groups, (of whatever name,) it is most 

 convenient to follow De Candolle's arrangement of them, in a gen- 

 eral way, with such minor alterations as may be called for. The 

 principal Floras now in use are arranged upon this general method. 

 It commences with the Exogenous class, with those orders of it 

 which are generally provided with complete flowers, and which ex- 

 hibit the floral organs in the most normal condition, according to 

 our theory of the blossom (Chap. IX., Sect. I. - III.), that is, 

 which have most of the several parts free and separate. It pro- 

 ceeds to those which are characterized by the union or consolida- 

 tion of their floral organs, and then to those which are reduced or 

 simplified by the suppression or obliteration of parts, ending with the 

 Gymnospermous subclass, the flowers of which are extremely simpli- 

 fied. The Endogenous class succeeds, with a somewhat analogous 

 arrangement, ending with Grasses ; and the classes of the Cryp- 

 togamous series follow in the order of their rank. 



736. The following cursory sketch takes in the principal orders, 

 freely omitting, however, small and obscure ones, as well as certain 

 well-characterized groups which have no interest to the ordinary 

 student, and no indigenous, naturalized, or commonly cultivated rep- 

 resentatives in the United States. Certain exotic orders are also 

 omitted from the synopsis of the classes or large divisions, for greater 

 simplicity, but are briefly mentioned in their proper place. Fuller 

 accounts of the natural orders, and of their systematic arrangement, 

 structure, properties, &c, must be sought in more extensive works, 

 such as Lindley's Vegetable Kingdom, De Candolle's Prodromus, &c. 

 As applied to the botany of this country, what is essential is comprised 

 in the Manual of the Botany of the Northern United States, by the 

 present writer, and in similar Floras. The characters of the orders, 

 &c. are drawn up in ordinary botanical language. For explanation 

 of the technical terms used, the reader may consult the Glossary at 

 the end of the volume. 



