INDEX. 851 



Grafting clay, its use in preventing evaporation and affording 



aqueous food for the scion, 235. 

 Grafting plasters, their 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, 278. 

 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. 



