leaf is deeply lobed. It is then either a Viburnum or an Acer, 

 and the fact that the leaf-margin is lobed and not finely serrate 

 brings the chase down to Acer. Before going further go back 

 over the key and make careful note of the particular characters 

 which were used to separate this genus from the other genera 

 and try to fix these in mind. This done, turn to the page indi- 

 cated, where you will find a Summer Key to the Species of Acer. 

 You run through this key in the same manner that you did the 

 genus key. If you have been careful in your search you will 

 finally stop at Acer saccharum. Once more pause and go back 

 over this key and try to fix in mind the characters which were 

 used to separate the various species, especially the difference 

 between your tree and Acer platanoides, which it so closely 

 resembles. This done, turn to the page indicated and compare 

 the characters of your tree with the drawings and descriptions. 

 If you are satisfied with your diagnosis, well and good. If you 

 find that you are wrong, go over the keys again and find wherein 

 you were led astray. 



Before you leave the tree take a sample of leaf properly 

 labeled which you can press between the pages of an old magazine 

 and save for future reference. Do this with other trees which 

 you may find and when you get home lay them out side by side 

 so that the labels will not show and compare them. A few trials 

 of this kind will serve to form a mental picture of each lea'f 

 which you will remember. 



A very helpful practice for the beginner is that of making 

 keys based upon various characters. Practice keys of this kind 

 will bring out the differences and likenesses of trees as will no 

 other means, and characters which have hitherto escaped the eye 

 will be prominently brought forward. Nor should the student 

 take his characters from books., but rather should he go to the 

 woods and get his knowledge first hand. 



It is hardly necessary to state that the key is a valuable 

 crutch while learning to walk, but once the leg is strong enough 

 to bear the weight it should be discarded, lest it become a burden. 

 A key 'has for its main object the guidance of the student through 

 the preliminary steps leading to a more intimate knowledge of the 

 trees. When once he knows a tree, instinctively, because of long 

 acquaintance with it, just as he knows people, then the need for 

 a key will have ceased. 



xx 



