The Trees of Vermont 13 



ARTIFICIAL KEYS, HOW MADE AND USED 



An artificial key is a scheme for identifying any unknown object 

 under consideration easily and quickly. This bulletin being devoted 

 to the trees of Vermont, its keys are intended to make it possible for 

 any person, even if his botanical training be meager, to determine what 

 native trees grow about his home or farm or in any Vermont city park 

 or woodlot. With certain modifications and within limitations they 

 may prove useful in other localities as well. 



Since many people are unfamiliar with the construction and use 

 of keys for purposes of identification, it is the purpose of the following 

 paragraphs briefly to outline the principles upon which they are built 

 and the manner in which they are used. 



The keys are based on the most striking similarities and differences 

 manifested by the various parts of trees — twigs, buds, leaves, etc. — that 

 is to say, those characters which stand out in bold relief, which catch 

 the eye at first sight. Two alternatives are presented, either a character 

 is or is not presented ; these are the only choices possible. Indeed, 

 further divisions are unnecessary and lead only to confusion and pos- 

 sible oversight. The two diametrically opposed characters are said to 

 be coordinate in rank. In the keys they are preceded by the same letter 

 or letters (a and aa or b and bb, etc.) and are set at the same distance 

 from the left margin of the page. Often a and aa, or b and bb are 

 divisible further into other groups ; in every case the characters are 

 opposed (a positive and a negative) and are given coordinate rank. It 

 is desirable for mechanical reasons to divide the main divisions of the 

 key more or less evenly, but this is not always feasible, nor should it 

 be adhered to strictly. 



The nature and use of a key may be made the more clear by a 

 homely but concrete example. Let us suppose that it is desired to 

 construct a key in order to distinguish from one another five houses in 

 a city block. Three of these houses are built of wood, two of brick, 

 and of the three wooden houses two are painted white and one brown. 

 We may classify them as follows : 

 a. Houses wood. 



b. Body paint brown Smith's house 



bb. Body paint white. 



c. Trimmings green color Jones' house 



CO. Trimmings slate color Brown's house 



aa. Houses brick. 



b. Roof gray slate Johnson's house 



bb. Roof red tile Public library 



