10 CONTEIvT; ANh 



CHAPTER XL — THE STEM, OR ASCENDING AXIS. — 69. 



161, Definition, — a, cause of its ascent. 162, Direction horizontal — erect — pro- 

 cnmbent — ascending — subterranean. 163, Annual — perennial. 164, Distinction 

 in regard to size, &c. — a, tree — 6, shrub — c, herb. 165, Most distinctive property 

 of stem. 166, Buds. 167, Leaf-bud. 168, The scaly envelopes, a, Scales not 

 formed in hot climates, &c. — their design. 169, Bud terminal, develops a simple 

 axis, — a, axillary, developes branches, — 3, adventitious. 170, Branch. 171, 

 Thorn, — a, its nature, &c. — 6, distinguished from prickles. 172, Node — inter- 

 node, — a, how formed — why the axis diminishes upwards. 173, AiTangement of 

 branches, — 174, spiral, — a, modifications — circular, how caused. 175, Alter- 

 nate — opposite — whorled. 176, Same of the branches. — a, Two classes of stems. 

 177, SubteiTanean — stemless plants — varieties. 178, Bulb, — a, tunicated — 

 scaly, — 5, how renewed, — c, bulblets. 179, Conn. ISO, Tuber. 181, Khizoma. 

 182, Creeper, — a, repent stems, their use. 183, Varieties of aerial stems. 184, 

 Caulis. 185, Eunner. 186, Scape, — a, culm. 187, Vine — a, tendril. 188, Twin- 

 ing stems — their direction. 189, Trunk — a, its dimensions. JVote, Illustrations, 

 6, its duration. Note, Illustrations. 190, Sucker. 191, Offset. 192, Stolon. 193, 

 Plurality of trimks — a, Banyan — Mangrove. 



§1. PHYSIOLOGICAL STRUCTURE OF THE EXOGENOUS STEM. — 77. 



194, Structure of herbaceous stems — 195, of the first year's growth of perennial 

 stems, — a, basis of the distinction of Exogens and Endogens. 196, Exogens. 197, 

 Endogens. 198, Parts of the exogenous structure. 199, Pith. 200, Medullary 

 sheath. 201, Wood — number of layers. 202, Layer consists of, — (7, arrangement 

 of its parts. 203, Alburnum — duramen. 204, Medullary rays. 205, Bark, — its 

 parts. — 206, its structure — cork — liber. 207, New layer, how formed, — a, outer 

 layers, why shaggy — horizontal fibres, — b, qualities resident in, — c, its peculiar 

 vessels. 



§2. FUNCTIONS OF THE STEM. — 80. 



208, Conveyance of sap, — 209, through "what portion — its course — elabonu 

 tion — descent. 



§3. OF THE ENDOGENOUS STRUCTURE.— 81. 



210, Its peculiarity. 211, Composition. 212, Each bundle consists of, — a, mod© 

 of increase. 



CHAPTER Xn.— THE LEAF.— 82. 



213, Its importance — character. 214, How distinguished. 215, Color — autum- 

 nal hues, — a, due to what — chlorophyll — changes, — b, color of flowers. 



Jl. VERNATION.— 82. 



216, Meaning of the term — leaf-bud how compacted, — a, illustration. 217, 

 Forms of vernation, — 1, Equitant — 2, Obvolute — 3, Involute — 4, Kevolute — 5, 

 Convolute — 6, Plaited — 7, Circinate. 



}2. ARRANGEMENT.— 83. 



218, In the bud — after the axis is developed, — 1, Scattered — 2, Alternate — 3, 

 Opposite — 4, VerticUlate — 5, Fasciculate. 219, How these forms may be reconciled 

 with the spiral, — a, illustration, — b, Alternate explained, — c, Opposite or whorled 

 explained. 220, Leaves radical — cauline — ramiEd. 



§3. ORGANOGRAPHY. — 84. 



221, Nature of the leaf — lamina — sessile — petiolate. 222, Petiole — its form — 

 1, Compressed — 2, Winged — 3, Amplexicaul. 223, General form of the lamina — 

 base — apex. 224, Leaf simple — compound. 225, Physiology. 226, Venation — 

 its organs. 227, Midrib — nerves. 228, Veins — veinlets. 229, Modes of venation. 

 1, Reticulate — 2, Parallel — 3, Forked. 230. Varieties of reticulate venation, — 1, 

 Feather-veined — 2, Radiate-veined — 3, Varieties of parallel venation. 



M. FORM OR FIGURE — 86. 

 231. Theory of— form dependent on venation. 232, Forms resulting from the 



