INDEX. 359 



Scion influenced by the stock, 224. 



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



129 — of oiled paper, 165. 

 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, 339 — 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, 75 — their formation favoured by a high tempe- 

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

 Seedlings, pricking out of, 268. 

 Seed, its nature, 7 — Hb 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, 7 6 



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



>j>j 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 of, 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 of, 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 unde* 

 which they are matured extends to the progeny, 299. 



