INDEX. 859 



Scion influenced by the stock, 324. 



Screens, 137 — their importance in moderating the dryness of the air, 

 129^-of oiled paper, 16S. 



Seasons of opposite extremes of moisture and dryness, 320. 



Secretion, saccharine, formed by the germinating seed, 10. 



Secretions of plants, formative agents of, 52 — an essential part of 

 them formed by the decomposition of carbonic acid, 389 — of the 

 fruit, 76 — changes which they undergo, 76 — result from the ac- 

 tion of their leaves, 52 — table of the proportions of carbon and 

 water in various, 76 — their formation favoured by a high tempe- 

 rature, with dryness, 83— decomposed by frost, 84 — of roots, 270, 



Seedlings, pricking out o^ 268. 



Seed, its nature, 7 — its properties of reproduction, 7 — are different 

 from those of leaf-buds, 7. 



Seeds contain an excess of carbon, 8 — ^manner of their germination, 8 

 — conditions required to produce their germination, 8. 



Seeds, germinating, form a saccharine secretion, 9 — those germinate 

 quickest which contain the most nitrogen, 20 — will renew the 

 species, 68 — will not produce the identical peculiarities which cha- 

 racterise varieties of the same species, 68 — origin of their food, 76 

 — their longevity, 77 — its cause, 77 — destruction of their vitality, 

 77 — ^remain dormant whilst their proportion of carbon is undis- 

 turbed, 77— difference in their vigour, 77, 161 — of tropical trees, 

 degree of heat required for germination, 103 — length of time 

 which some species o^ will lie in the ground, 168 — consequences 

 of gathering them in an unripe state, 175 — close packing of, in- 

 jurious in hot climates, 182 — containing oily matter, 184 — ex- 

 treme temperature which various species will bear, 162 — tem- 

 perature required for their germination, 162 — cause of their rot- 

 ting in the ground, 164 — vital energy o^ 164 — with very hard 

 integuments, means resorted to for assisting their germination, 

 164 — old, of spruce fir, germination promoted in, 167 — germi- 

 nating, effects produced upon, by alkaline substances, 166 — 

 subjected to boiling, 165 — weak, produce weak plants, 174— of 

 composite plants, 174 — period of their retention of the power 

 of germination, 175 — ripeness in, 176 — invigorated, 175 — their 

 preservation, 177 — reproduce species only with certainty, 296 — 

 ' preservation of races by, 296 — influence of circumstances ujider 

 which they are matured extends to the progeny, 299. 



