INDEX. 857 



Races of plants, improvement of, 806. 



Radiation, 138. 



Radicle, 10. 



Rain, amount of, at various places, 128. 



Repotting, 272. 



Reproduction, property of, in leaf-buds, '7 — ^properties o^ in seeds, 1. 



Respiration, a function performed by the leaves, 40. 



Rest of plants, 113 — periods of, in tropical regions, 321 — ^in tropical 

 regions, how imitated, 326." 



Resting plants, 319. 



Rind, 26. 



Ringing, an operation by which the production of roots is accele- 

 rated, 15 — experiments on, 34 — physiological nature of the 

 operation, 252 — ^its effects on fructification, 65 — its use in facili- 

 tating the production of roots, 208 — proper seasons for, 254 — 

 its effects with regard to fruit and flowers, 254 — its ultimate 

 consequences, 255. 



Ripening of seeds, 175. 



Root, substance from which it first derives its means of accretion, 

 10 — is the part soonest developed, 10 — mode of its increase in 

 length after it passes the embryo state, 1 1 — at first grows by a 

 general distension of its tissue, 11 — offices of its bark, 12 — its 

 proportion to the stem variable, 16. 



Roots lengthen at their points only, after passing their embryo 

 state, 11 — why their extreme points are called spongelets, 11 — 

 delicacy of their extreme points, 11 — their hygrometrical pro- 

 perties, 1 1 — ^local motions of their spongioles in quest of fresh 

 food, 13 — immediate cause of their formation involved in 

 obscurity, 14 — produced from various parts of plants, 14 — aug- 

 ment in diameter simultaneously with the stem, 14 — growing iu 

 air, 13 — growing in water, 13 — their formation, an elaboration 

 of organisable matter furnished by the leaves, 15. 



Acots perish if their formation be not speedily followed by the 

 development of leaves, 14 — most readily formed in darkness, 14 

 — produced by removing a ring of bark, 15 — differ from 

 branches in not being the development of previously formed 

 buds, 14 — their incessant activity arrested only when frozen, 16 

 — ^their principal office, 15 — their feeding property depends 

 upon the hygrometrical force of their tissue, 16 — absorb gene- 



