have long been recognized by botanists, viz., the Phaenogamia or Flowering Plants; the Cryptogamia, or Flowerless Plants. Besides the obvious distinction made by the presence and absence of the flower,

2, Rose (flowers double)   an Exogen

2, Rose (flowers double) - an Exogen. 3, Lily - an Endogen. 4. Form - an acrogenous Cryptogam. 5, Lichen - a thallogenous Cryptogam.

66. These Grand Divisions are further distinguished by their organic structure and general aspects. In the Phsenogamia we find a system of compound organs, such as root, stem, leaf, bud, flower, successively developed on a determinate plan; while in the Cryptogamia, a gradual departure from this plan commences, and they become, at length, in their lowest forms, simple expansions of a uniform tissue, without symmetry or proportion. This distinction is rendered perfectly clear by a reference to

67. Examples. Compare a rose with a fern. In the former a regular axis bears buds which are unfolded, some into leaves, others into flowers succeeded by fruit. In the fern no buds nor flowers appear, and the fruit dots sprinkle over the back of the leaf. Again, contrast the violet with a lichen, where neither stem, root, nor leaf appears, much less flowers, but disc-like expansions with fruit-dust (spores) produced indifferently in any part of them.

68. Subdivisions of the Phaenogamia. This grand division is itself very naturally resolved into two subdivisions, named by De Candolle Exogens and Endogens.

69. Exogenous plants or Exogens (outside-growers), including all the trees (except palms) and most herbaceous plants of temperate regions, are so named, because the additions to the diameter of the stem are made externally to the wood already formed.

70. Endogenous plants or Endogens (inside-growers), including the grasses and most bulbous plants of temperate climates, and the palms, canes, etc., south, are so named from the accretions of the stem taking place within the parts already formed.

71. These subdivisions are more accurately distinguished by the structure of the seed. The seeds of the Exogens consists of two equal seed-lobes, called cotyledons, as seen in the pea. The seed of the Endogens consists of but one seed-lobe or cotyledon, as in the Indian Corn. On this account Exogens were first called Dicotyledonous (two-cotyle-doned) plants, and Endogens, Monocotyledonous (one-cotyledoned) plants; - names quite appropriate, but too hard and long for general use.

72. They are also very readily distinguished by their leaves, which arc net-veined in the Exogens, and parallel-veined in the Endogens. Moreover, their flowers are remarkably different, being almost always three-parted in the latter and about five-parted in the former. But all these distinctions, with some others,will be more definitely stated hereafter.

73. The Name of a plant or other natural object is twofold, - the trivial or popular name, by which it is generally known in the country; and the Latin name, by which it is accurately designated in science throughout the world. For example, strawberry is the popular name, and Fragaria vesca the Latin or scientific name of the same plant.

74. In elementary treatises, like the present, for the sake of being readily understood, plants are usually called by their popular names. Yet we earnestly recommend to the learner to accustom himself early to the use of the more accurate names employed in science.

75. The Latin name is always double; - generic and specific. Thus Fragaria is generic, or the name of the genus of the plant, vesca is specific, or the name of the species.

76. A Species embraces all such individuals as may have originated from a common stock. Such individuals bear an essential resemblance to each other as well as to their common parent, in all their parts.

77. For example, the white clover (Trifolium repens) is a species embracing thousands of cotemporary individuals scattered over our hills and plains, all of common descent, and producing other individuals of their own kind from their seed.

78. Varieties. To this law of resemblance in plants of one common origin there are some apparent exceptions. Individuals descended from the same parent often bear flowers differing in color, or fruit differing in flavor, or leaves differing in form, etc. Such plants are called varieties. They are never permanent, but exhibit a constant tendency to revert to their original type.

79. Examples. Varieties occur chiefly in species maintained by cultivation, as the apple, potato, rose, Dahlia. They also occur more or less in native plants (as Hepatica triloba), often rendering the limits of the species extremely doubtful. They are due to the different circumstances of climate, soil, and culture to which they are subjected, and continue distinct only until left again to multiply spontaneously from seed in their own proper soil, or some other change of circumstances.

80. A Genus is an assemblage of species closely related to each other in the structure of their flowers and fruit, and having more points of resemblance than of difference throughout.

81. Illustration. The genus clover (Trifolium) includes many species, as the white clover (T. repens), the red clover (T. pratense), the buffalo clover (T. reflexum), etc., agreeing in floral structure and general aspect so obviously that the most hasty observer would notice their relationship. So in the genus Pinus. no one would hesitate to include the white pine, the pitch pine, the long-leafed pine (P. strobus, rigida, and palustris), any more than we would fail to observe their differences.

82. Thus individuals are grouped into species, and species are associated into genera. These groups constitute the bases of all the systems of classification in use, whether by artificial or natural methods.