AT THE PERIOD OF PUBERTY. 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: 



Age at the 

 Height in feet. time of flowering. 



Norway Spruce (Abies excelsa),. . . 80 to 120 50 years. 



Silver Fir (Abies pectinacea], . . . 80 to 100 30 " 



Elm ( Ulmus Americana], . . . . 60 to 80 40 " 



Hornbeam (Carpinus Americana), . 10 to 20 20 " 



Linden (Tilia Americana}, . . . 60 to 80 25 to 30 years. 



Maple (Acer rubrum], . . . . 15 to 20 25 to 30 " 



Birch (Betula alba], 30 to 40 10 to 12 " 



Chestnut (Castanea vesca], . . . 60 to 80 25 to 30 " 



Beech (Fagus ferruginea], . . . 60 to 70 40 to 50 " 



Larch (Larix Americana], . . . 40 to 60 15 " 



Ash (Fraxinus pubescens], . . . 50 to 60 25 " 



Hazel (Corylus Americana], . . 4 to 8 10 " 



Oak (Quercus alba], 40 to 60 50 to 60 " 



Hickory ( Carya alba], . . . . 40 to 50 25 to 30 " 



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- 



