6 Bulletin 194 



etc., each with its characteristic ending. Thus, Acer saccharum nigrum 

 (Michx. f.) Britt. is classified as follows: 



Division — Spermatophyta 



Subdivision — Angiospermae 

 Class — Dicotyledoneae 

 Order — Sapindales 



Family — Aceraceae 

 Genus— Acer 



Species — saccharum 

 Variety — nigrum. 



Habit. — Habit, or the general appearance of a plant, is an impor- 

 tant character of identification, especially as we become more and more 

 familiar with the trees. Two main types are recognized, based on the 

 manner of the branching of the trunk, the upright and the spreading. 

 In the one the trunk extends straight upwards without dividing, as is 

 typical in most of the conifers; in the other the trunk divides to form 

 several large branches and the broad, spreading crown of most of our 

 broad-leaf trees. In either case the crown may be regular in outline 

 or very irregular, straggling or straight-limbed. Moreover, the tree 

 growing in the open, where there is no crowding and plenty of light, 

 may dififer greatly from the tree in the forest, where the struggle for 

 existence becomes very keen. A short, thick trunk and a low, spread- 

 ing, many-branched crown characterize the tree in the open, whereas 

 the forest tree has a long, slender, clean trunk and a narrow crown of 

 few branches. In the descriptions of trees in this bulletin, unless other- 

 wise stated, the habit in the open is the one given. Again, the tree may 

 have been injured by storm or insect at some period of its growth and 

 its natural symmetry destroyed. Moreover, the age of a tree has a 

 great influence on its outline, young trees generally being narrow and 

 more or less conical, broadening out as they become older. We may 

 say, then, that each tree has an individuality of its own, little eccentrici- 

 ties similar to those that make people different from one another. And 

 just as we have little difficulty in recognizing our friends at a distance 

 by some peculiarity of walk or action, so we are able to recognize 

 many trees at a distance by some peculiarity of form or habit. 



Leaves. — With the advent of spring the buds of our broad-leaf 

 trees swell and burst and the leaves come forth and clothe the trees 

 with mantles of green, hiding the branches which have been bare 

 through the cold winter months. The evergreens, too, take on fresh 

 color and commence a new period of growth. The beginner in botani- 



