REPRODUCTIVE POWER. 65 



The greater the production of seed, and the better its 

 quality, the more assured is reproduction ; both quantity 

 and quality of the seed depend on the age of the trees, the 

 locality, the available light and the species. 



(1.) Age. — The first point of interest is the time when the 

 various species commence to produce seed fit to germinate. 

 Apart from single trees here and there, the average period 

 may be placed as follows,* in the case of trees grown in 

 regular woods : — 



At the ar/e of 25 — 30 j/eais: Mountain pine, birch, white 

 alder, aspen, acacia. 



At the afie (>/" 30 — 40 yeitis: Scotch pine, Austrian pine, 

 Weymouth pine, larch, Norway maple, common alder, 

 lime, horse chestnut. 



.4^ tJte aijc of 40 — 50 ijcarn : Hornbeam, elm, ash, 

 sycamore. 



At the age <f 50 — 60 i/ears : Spruce, sweet chestnut. 



At the age o/'60 — 70 ijears : Beech. 



At the age of 70 — 80 gears .- Silver fir, Cembran pine, oak. 



The most favourable age for the production of seed is, 

 ordinarily, that when the principal height growth is about to 

 be completed, and when an extension of the crown takes 

 place ; in other words, when the individual tree lays on its 

 maximum volume growth. At that period the best seed is 

 produced. Younger trees produce larger but fewer seeds ; 

 older trees produce more numerous but smaller seeds. 



(2.) Localitg. — Temperature is of first importance ; where 

 that is deficient, the production of seed is seriously endangered. 

 Tree seeds contain a comparatively large proportion of ash, 

 and their production necessitates increased assimilation of 

 substances from the soil; hence, fresh fertile soils produce 

 more and better seed than poor soils. A crop of seed also 

 requires large quantities of nitrogen, the supply of which is, 

 in consequence, much exhausted. 



Some species no longer produce seed fit to germinate (or 



* According to Hess. 

 S. F 



