EXPLANATION OF THE PLAN OF THE HANDBOOK. 



In the illustrated portion two pages which face each other are devoted to 

 a species, practically all of the well-detined species within the area indicated 

 being included. The few exceptions will be found mentioned after their 

 respective genera. (See pages 418— i57.) 



It will be observed that the background in the pictures of leaves, fruits and 

 twigs are marked into squares. These are lines in all cases one inch apart; 

 their deviation from that measurement, in the picture, indicating a propor- 

 tional enlargement or reduction of the object, in order to make the plates of 

 uniform size. On viewing the picture with the standard of measurement in 

 mind the actual size of the object is at once evident. 



The trees selected as subjects for pictures of barks are generally of medium 

 size, as showing the phase of bark most commonly seen, and are such as could 

 be called characteristic examples. The measure placed upon the trunks before 

 photogvaphing, to indicate size, is one foot in length, excepting when otherwise 

 stated. 



On the outline maps the shaded areas indicate the regions over which the 

 trees are distributed, as indicated by outlying representatives, as nearly as is 

 generally understood. Within the limits of such areas there are often tracts, 

 of greater or less extent, where the tree in question is not found, on account 

 of unfavorable conditions of altitude, perhaps, or of soil, moisture, etc., or of 

 other less evident reasons. Such limited tracts could not be easily indicated 

 on our much reduced maps. It cannot be claimed of these maps that they are 

 alwavs absolutely perfect, as trees may sometimes be found outside the areas 

 generally accredited to them. In view of further perfecting the maps, for 

 futiTrc use, the author would be obliged for whatever data the observers of trees 

 may have and find it convenient to send that would be important to have in 

 this connection. 



The wood-structure pictures represent transverse sections (the end view of 

 the grain) magnified uniformly about fifteen diameters. That is approxi- 

 mately' the magnification secured by a good simple magnifier. Such a glass is 

 quit'^ essential in identifying woods, hx comparison, having first exposed the 

 end of the grain with a shar]i knife to reveal its structure. 



In The foot-notes, following the letter-press on the right-hand page, will be 

 found such SATionyms only as are used in recent works, where the names there 

 adopted differ from the names used in this work. " A. W." indicates 

 AMERICAN WOODS, in which work the species is further considered, 

 especiallv with reference to its woods, and in which actual si^ecimens of same 

 may be seen. The Eoman numeral indicates the part or volume in which a 

 species is foimd and the Araliic numeral its serial number. (See pages follow- 

 ing the index at close of this volume.) 



[vii] 



