42 ELEMENTS OF BIOLOGY. 



Each half of the lower jaw composed of several pieces. Appendages of 

 the skin in the form of homy scales or bony plates. 



Class D. Aves (Birds). — Respiratory organs in the form of lungs. 

 Lungs connected with air-receptacles placed in various parts of the 

 body. Heart four- chambered. Blood warm. Skull connected with 

 the backbone by a single articulating surface or ' ' condyle." Each half 

 of the lower jaw composed of several pieces. Appendages of the skin 

 in the form of feathers. Fore-limbs converted into wings. Animal 

 oviparous. 



Class E. TvLvmmalia (Quadrupeds). — Breathing organs in the form 

 of lungs, which are never connected with air-receptacles placed in 

 different parts of the body. Heart four- chambered. Blood \varm. 

 Skull connected with the backbone by two articulating surfaces or 

 "condyles." Each half of the lower jaw composed of a single piece. 

 Appendages of the skin in the form of hairs. Young nourished by 

 means of a special fluid — the milk — secreted by special glands — the 

 mammary glands. Animal viviparous. 



VEGETABLE KINGDOM. 



Sub-Kingdom I.— Cryptogams, 



Plants destitute of true flowers with stamens and pistils. No tru^ 

 seeds, but simple cellules or " spores," in which there is no embryo 

 prior to germination. 



Class I. Thallophyta.- — Stem and foliage undistinguishable, com- 

 posed of cellular tissue only. Ex. Lichens, Algae, and Fungi. 



Class II. Anophyta. — Stem and foliage distinct or confluent, of 

 cellular tissue only. ^x. Mosses and Liverworts. 



Class III. Acrogens. — Stem with woody tissue and vessels, growing 

 at its summit, and usually with distinct foliage. Ex. Horse-tails, Club- 

 mosses, Ferns. 



Sub-Kingdom II. — Phanerogams. 



Plants producing true flowers with stamens and pistils. True seeds 

 containing an embr}'o. 



Section A. Monocotyledones. — Seeds with one cotyledon or seed- 

 leaf. Stems '■'endogenous,^'' toith no manifest distinction into bark, wood, 

 aiid pith. 



Class I. Endogens. — Leaves parallel- veined, permanent. Root 

 like the stem internally. Ex. Palms, Lilies, Grasses. 



Class II. Dictyogens. — Leaves net-veined, deciduous. Root 

 with the wood in a solid concentric circle. Ex. Sarsaparilla. 



