CHAP, in.] * Characteristics of Trees 63 



The formation of seed depends on the supplies of starchy and 

 nitrogenous reserves stored up in the tree. These vary according 

 to its age, the soil and situation the amount of exposure to light, 

 and the warmth of the summer period of vegetation. In good 

 seed-years Beech, Oak, Spruce, Pine, Birch, Hornbeam, Elm, 

 Aspen, Alder, and Willow produce larger quantities of seed 

 than Ash, Maple, Sycamore, Silver Fir, and Larch. But, 

 classifying them as to the total quantities of seed produced 

 during long periods, it may be said that Birch, Aspen, and 

 Willow are most prolific ; next to them come the Pines, 

 Spruces and Douglas Firs, Elm, Hornbeam, and Alder ; behind 

 these again rank the Oak, Maple, Sycamore, Silver Fir, Larch, 

 and Ash whilst last of all in this respect comes the Beech. 



From this it cannot fail to be noted that in general the 

 species with small seeds are more prolific than those with 

 large and heavy fruits. As these light, and very often winged, 

 seeds are more easily wafted and borne far away by winds, 

 it must be admitted that species of trees like Birch, Aspen, 

 Pine, and Spruce have better natural reproductive power than 

 Oak, Beech, Silver Fir, and the like. It is worthy of note, 

 too, that the former are species which make less demands on 

 soil fertility than the latter, and are at the same time endowed 

 with greater accommodative powers as to soil and situation ; 

 for these are matters almost sure to be closely connected with 

 the power of accumulating reserves of starchy and nitrogenous 

 substances utilizable for the formation of flowering-buds. 



The different kinds of seeds vary, however, greatly in their 

 germinative power. This is lowest in Birch, Alder, Elm, and 

 Larch. It amounts to about 50 % in Ash, Hornbeam, Maple, 

 Sycamore, Weymouth Pine and Silver Fir ; whilst it is some- 

 what greater in Oak, Beech, Spruce, and Scots, Corsican, and 

 Austrian Pines. 



The seed of most species of trees germinates in the spring 

 after it has been shed ; but that of Birch, Elm, Aspen, and 

 Willow sprouts during the spring in which it falls, and that of 



