AT THE PERIOD OF PUBEETT. 



157 



continue to flower and fruit for a number of years, without 

 showing any signs of decay, or any indications whatever of 

 diminished vitality. 



Each species of tree, however, has its own period of time 

 during which it vegetates, so as to gain the requisite 

 strength for reproduction, although the time varies with 

 the favorable or unfavorable circumstances in which the 

 tree may be placed, such as suitable soil, and exposure to 

 the sun's influence. The following examples will illustrate 

 the difference in the maximum growth and age, at the 

 time of flowering, of some of our principal trees : — 



Norway Spruce (Abies excelsa), . 

 Silver Fir (Abies pecHnacea), . 

 Elm ( JJlmus Americana), . 

 Hornbeam ( Carpinus Americana), 

 Lindea (Tilia Americana), 

 Maple (Acer rubrum). 

 Birch (Betula alba), . 

 Chestnut (Castanea vesca) 

 Beech (Fagus fefrruginea), 

 Larch (Larix Americana), 

 Aah (Fraxinus pubescens). 

 Hazel ( Corylus Americana), 

 Oak (Quercus alba), . 

 Hickory ( Carya alba), 



Height in feet, 



80 to 120 

 80 to 100 

 60 to 80 

 10 to 20 

 60 to 80 

 15 to 20 

 30 to 40 

 60 to 80 

 60 to 70 

 40 to 60 

 50 to 60 

 4 to 8 

 40 to 60 

 40 to 50 



Age at the 

 time of flowering. 



50 years. 



30 " 



40 " 



20 " 



25 to 30 years. 



25 to 30 



10 to 12 



25 to 30 



40 to 50 



15 



25 



10 



60 to 60 



25 to 30 



it 

 it 

 II 

 it 

 li 

 It 

 tt 

 tt 

 tt 



The above numbers give the mean ages and height of 

 these trees at the time of flowering under the most favor- 

 able conditions, especially where the tree has plenty of 

 room for development, and the soil is suitable. 



In trees, as well as in herbaceous plants, vegetation is 

 checked by reproduction. Those branches which are 

 destined to exercise this function, take, at this time, a 

 short, stunted appearance, growing only a few inches or 

 lines in length in the same time that they formerly grew as 

 many feet ; the bud-traces on the outside of the branches 

 {gemma vestigia), the intervals between, which mark the 

 annual growths, thus become crowded together. Ulti- 



