FOR ARTIFICIAL REPRODUCTION. 54? 



1. Production of Seed hy different Species of Trees. 



A sufficiency of nutritive reserve-material, light and heat 

 are the chief causes of the i)roduction of fruit. A fair amount 

 of the annually assimilated material not employed in the con- 

 struction of new wood, is stored-up in trees, especially in their 

 medullary rays [also in the leaves of evergreen species.— Tr.]. 

 Once this reserve-material has attained a certain amount, the 

 tree can blossom and produce fruit. Nearly all the reserve 

 material in a tree is exhausted during a seed-year, and it 

 then again commences storing a fresh supply. A warm, di-y, 

 sunny growing season when the tree produces little wood, is a 

 condition for blossoming in the succeeding year. When once 

 the inflorescence-buds are formed, the weather during the 

 blossoming period will decide matters (absence of frost in the 

 daytime, &c.) ; in the case of species which require much 

 heat the succeeding summer weather may cause the fruit to 

 ripen, or may not be sufficiently warm for the purpose, and at 

 any rate will affect its comparative abundance or scarcity. For 

 a plentiful seed-year, therefore, two successive warm years are 

 required ; cold years and especially wet and cold years are never 

 rich seed-years, or produce much useless seed. This rule is not, 

 however, universal, and there is much difference in this respect 

 among dift'erent species of trees. 



Thus, in the case of beech, a preliminary warm, dry year is 

 more important than the state of the weather in the actual seed 

 year. Once the inflorescence-buds are formed and the spring 

 passes without damage by frost, the beech-mast will ripen, even 

 when the summer is unfavourable (for instance in 1877, 1882, 

 1888). For the oak, on the contrary, the seed-year must be 

 warm and dry ; hence, years of plentiful acorns coincide with a 

 good vintage, whilst beech-mast years follow one. For the oak, 

 therefore, the formation of good inflorescence-buds is readily 

 effected, the open oak forest obtaining more light and heat than 

 dense beech -woods. 



The natural period for fruiting is the latter part of the 

 pole-stage and the commencement of maturity, when trees 

 have attained their full height and are growing vigorously in 

 girth. This period is termed fertility, and its earlier or 



