Possible Errors. In using this book, care must be taken to com- 

 pare all the lines under each number with the plant, and to use judg- 

 ment in selecting the right one. While faulty observation or poor 

 judgment may lead to error, a mistake is usually due to carelessness 

 in not following correctly the reference at the end of the line chosen. 

 If one reaches a number in which none of the lines of description 

 agrees with the plant, it is very probable that he has made a mistake 

 at an earlier stage of the identification, and he should then begin anew. 



It has been the intention of the author to make the key as nearly 

 as possible proof against errors of judgment. For example, the Indian 

 Turnip may be sought under either Group 3 or Group 4 ; the Matrimony 

 Vine may be identified either as a shrub or as an herb, and numerous 

 other similar examples may be discovered. 



Botanical Information Needed. It is presumed that those using 

 the book will be familiar with the parts of the flower and with the 

 commoner descriptive terms applied to leaves. Unusual terms have 

 been avoided as far as possible, but those which do occur, as well as 

 the simpler ones, are explained in the glossary. 



In general, only those characters have been used in the keys 

 which can be observed without a magnifying glass and without dis- 

 section of the flower. 



In several groups of plants, reference is made to the fuller descrip- 

 tions to be found in the Manuals. The standard manuals for Michigan 

 are Gray's New Manual of Botany, 7th edition (American Book Com- 

 pany, $2.50), and Britton and Brown, Illustrated Flora of the Northern 

 States and Canada (Chas. Scribner's Sons, $13.50). These books may 

 be consulted in most school or public libraries. 



All dimensions are expressed in the metric system. For con- 

 venience, it may be stated that 25 millimeters (mm.) are about equal 

 to one inch; 1 centimeter (cm.) to two-fifths of an inch; 1 decimeter 

 (dm.) to 4 inches; and 1 meter (m.) is a little more than 3 feet. 



