DATES OF SEEDBEARING. 669 



Cypresses, as well as Thuya and Chamaecyparis, form their 

 small, slightly-winged seeds in little cones, or strobiles, the 

 scales of which open soon after they ripen ; in Junipers the 

 scales have grown together into a berry ; in Yews (Taxu-s) the 

 nut-like seed is surrounded by a red, fleshy aril. 



SECTION II. DATES OF SEEDBEARING AND ITS REPETITION. 



Usually woody species that have the lightest seeds are the 

 earliest seedbearers : thus willows, poplars, birches, alders 

 and elms are earliest, while oaks and beech are latest ; between 

 these extremes come the other broadleaved species. The larch 

 among conifers has the earliest seeds, and has also the lightest 

 of our coniferous seeds. Where Thuya and Chamaecyparis 

 grow, they have the lightest of coniferous seeds, and normally 

 produce seed from very young trees ; silver-fir and Cembran 

 pine have heavy seeds, and produce seed later in life. When 

 the seeds of two or more species are of about equal weight, 

 that which is light-demanding bears seed earliest ; thus pines 

 produce seed earlier than spruces, and oaks before beech. 



Exposure to light also determines early seed-bearing ; 

 trees in the open bear seed 20 to 30 years earlier than the 

 same species in a dense crop, the crowns of which are illu- 

 minated only at the top. Interruption of cover is therefore the 

 best way of inducing a tree in a wood to bear seed. Heat is 

 next to light the most important factor ; in warm localities the 

 same species bears seed earlier than in cool localities. A good 

 soil, on which a tree grows rapidly, delays the production of 

 seed, whilst bad soil, where the trees grow slowly, accelerates 

 seed-bearing. 



The grower of fruit-trees makes use of this latter property, 

 by pruning the trees or by altering the conditions of the soil, 

 in order to compel a tree to bear fruit early. 



When the formation of fruit has commenced, it does not 

 recur every year, but after definite intervals. E. Hartig has 

 explained this periodicity of seed-bearing by the fact, that at 

 the commencement of a seed-year, much of the reserve-material 

 (starch) of the sapwood is dissolved, so that a number of 

 years is required for replacing the starch ; as soon as sufficient 



