INDEX. 351 



Grafting clay, its use in preventing evaporation and affording 



aqueous food for the scion, 235. 

 Grafting plasters, thei r unfitness to supply aqueous food to scions, 2S5. 

 Grass, its fibrous texture favourable to the emission of heat, 137. 

 Granulation, 282. 



Granulations of cellular tissue, 235 — formed by the living tissue, 293 

 Grapes, a cause of their shrivelling, 106. 

 Greenhouse plants, their exposure, 273. 

 Growth by the stem, 22. 

 Growing point, 22. 



H. 



Heart-wood, its mode of formation, 27 — the oldest formation, 27. 



Heat, its impulse to the vital principle, 9 — necessary to produce 

 germination, 8 — produces a distension of all the organic parts, 9 

 ^-degree of, most conducive to germination, is variable, 9 — its 

 agency in changing the secretions of fruits, 74 — the stimulus of 

 excitability, 87 — acts as a stimulus to the vital forces, 107. 



Herbaceous grafting, 236. 



Horizontal plane, bad effects of training on a, 257 — system, 214. 



Horizontal cellular system, 282 — systems of stocks and scions, neces- 

 sity for their correspondence in growth, 222. 



Hothouses, causes of atmospheric dryness in, 143. 



Hot springs, their effects on surrounding vegetation, 103. 



Hybrids, their origin, 68 — are generally sterile, 69. 



Hydrogen, fixed in the tissue of plants, 8 — excess of, in certain vege- 

 table secretions, 75 — incorporated in the tissue of plants, deri- 

 vation of its supply, 18. 



Hygrometers, 126 — Daniell's, 126. 



Improvements in the races of plants by direct means, 307 — ^by indi 

 rect means, 309. 



Inarching, 238 — circumstances conducive to its success, 239. 



Inner bark, 24. 



Insects, 124 — their ravages on vegetables, preventive o^ 124 — con- 

 ducive to fertilisation, 172. 



Iron roofs for plant-houses, light afforded by, S26. 



