600^ 



INDEX. 



Sapwood, and mode of its formation, 40 

 Saturation, hygrometrical, 1 84 

 Saw-dust as manure, 565 

 Scales, propagation by, 273 

 Scion affects the stock, 358 



and stock, example to show their 



mode of adhesion, 343 



■ should be well suited to 



each other, 351 

 effects of the stock on, 353 



influenced by the stock, 303 



Scions, how to keep fresh, 342 



. — . from the trunk of a tree con- 

 sidered preferable to those 

 from the branches, 341 



should be more backward in their 



vegetation than the stocks, 339 

 Scorching, causes of, in damp houses, and 



mode of preventing, 208 

 Screens, form of, for guarding plants from 

 •wind, 189 



of oiled paper, 218 



their importance in modifying 



the dryness of the air, 186, 198 

 Seasons, alternations of, 116 

 — — — tropical, 132 

 Seaweeds, M. Thuret's experiments on 



the spores of, 10 

 Secretions, an essential part of them 

 formed by the decompo- 

 sition of carbonic acid, 

 545 



, are generated faster by the 



aid of heat, 277 



are improved-in quaiity when 



air has the fullest access to 

 the plants, 101 



of plants, formative agents of, 



70 

 result from the ac- 

 tion of their leaves, 

 70 

 their formation fa- 

 voured by a high 

 temperature with 

 dryness, 100 

 of the fruit, changes they un- 

 dergo, 100 



saccharine, formed by the 



germinatiug seed, 16 

 Seed, care required to save, 468 



its nature, 13 



its properties of reproduction dif- 

 ferent from those of the leaf- 

 buds, 13 

 Seedlings, health depends on that of the 

 seed, 474 



. Mr. Thompson's experience in 



regaird to, 506 

 — pricking out of, 432 



Seedlings, real quality of, cannot be ascer- 

 tained when first produced, 

 500 



Seeds, cause of their longevity, 103 



cause of their rotting in the 



ground, 247 



chemical changes in, 227 



- close packing of, injurious in hot 



climates, 249 



■ conditions requisite to produce 



germination, 13 



consequences of gathering them in 



an unripe state, 243 



degree of heat which some will 



bear, 247 



depth at which to sow, 228 



— — destruction of their vitality, 104 



difierence in their vigour, 104 



effect of boiling,, 106, 235 



effect of deoxydising, 236 



effect of electrical action on germi- 



nating, 15 



evils of deep sowing, 229 



excess of carbon in, 14 



germinating, effects of, under dif- 



ferent coloured glass, 238 



germinating, effects produced on, 



by alkaline substances, 235 



germinate from a saccharine secre- 



tion, 16 

 growing in air, 21 



influence of circumstances under 



which they are matured extends 

 to the progeny, 243 



invigorated, 243 



length of time they will remain in 



the ground without growing, 238 



manner of germination, 14 



of composite plants, 242 



old, of spruce fir, germination pro- 



moted in, 236 



old, of stocks, &c., produce double 



flowers, 502 



of tropical trees, degree of heat 



requiredfortheir germination, 135 

 — r- origin of their food, 103 



peculiar modes of sowing, 234 



period of their retention of the 



power of germination, 103, 246 



preservation of races by, 463 



remain dormant whilst their pro- 



portion of carbon is undimi- 

 nished, 104 



—. — renew the languid vigour of a 

 species, 472 



— ; — renewal by, not always a preventa- 

 tive of disease, 474 



reproduce species only with cer- 



tainty, 13, 95, 463 



ripeness in, 243 



