356 INDEX. 



soils, and others will not, 332 — aphyllous, office of leaves per 

 formed in, by the rind and epidermis, 40. 



Plumule, 22 —derives its nourishment partly from the cotyledons and 

 partly through the agency of the rt ot, 22. 



Plugging of potted plants, 273. 



Poisonous substances fatal to man prove equally so to plants, 17. 



Poisons, alkaline, their destructive effects, 18 — metallic, destructive 

 to plants, 18. 



Pollen, agents which affect its fertilising powers, 171 — deficiency of, 

 a cause of sterility in seeds, 171. 



Potash, employed to promote germination, 166— as a component of 

 .manures, 335, 338. 



Potato, tubers of, early varieties, their appropriation of nutritive 

 matter, 173 — means of obtaining improved varieties of, 308— 

 unequal periods of its maturity from different eyes, 189. 



Potatoes, disease of, curl in the leaves of, 73 — propagation of, from 

 eyes, 185. 



Pots for plants, their drainage, 119— double, for plants,' 274 — neces- 

 sity of their being proportioned to the size of the plants, 277. 



Potting, 267— objects attained by, 267 — cases in which it may be 

 advantageously dispensed with, 268. 



Preservation of races by seed, 295. 



Pricking out seedlings, 268. 



Principles upon which the operations of horticulture essentially 

 depend, 101. 



Productiveness, 64. 



Propagation by budding and grafting, only successful within certain 

 degrees of affinity, 222 — 'its objects, 224; 228— its rationale ex- 

 plained, 199, 225 — by cuttings, 195 ; — by knaurs, 189 — by layers 

 and suckers, 207 — by leaves, 189— by eyes, 184 — by eytes and 

 cuttings, difference of, from that by budding and grafting, 211 

 — by roots, depends on the formation of adventitious buds, 20. 



Protection afforded by walls, 266. 



Pruning, 289 — its objects, 239 — its effects, 248— seasons for, 247 — of 

 transplanted trees, 248 — of roots, 249. 



Pv. 



Races of plants, means of their preservation by seeds, 297 — means 

 of fixing their habits, 297— accidental alterations in, 807. 



