EXPLANATION OF THE PLAN OF THE HANDBOOK. 



In the illustrated purtiou two pages wliicli face each other are devoted to 

 a species, jivactically all of the well-dehued species within the area indicated 

 being ineliide(I. IMie few exceptions will he found mentioned after their 

 respecti\'e genera. (See pages il8-457. ) 



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

 twigs arc marked inln s(|uares. These are lines in all cases one inch apart; 

 their deviati(jn from that measurement, in the picture, indicating a propor- 

 tional enhirgemeni or reducti(.)ii of the object, in order to make tlie plates of 

 uniform size. On \dewiuii' the picture with the standard of measurement in 

 mind the actual ^ize of I be object is at once evident. 



The trees selected as sulijeets for pictures of barks are generallv 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 

 photogra})liiiig, to indicate size, is one foot in length, excepting when otherwise 

 stated. 



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

 trees are distributed, as indicated l.iy (lutlying representatives, as nearly as is 



generally underst I. Williin the limits of such areas there are often tracts, 



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

 of unfavorable conditions of altitude, jjerhaps, <jr of soil, moisture, etc., (n' of 

 other less e\'ideul I'casons. Sucli limited tracts could not be easily indicated 

 on our much reduced ma])s. Jt cannot lie claimed of these maps tluit tliey are 

 always absoluteh' perfeel, as trees may sometimes lie found outside the areas 

 generallv aecre(lited to them. lu ^dew of further jierfecting the maps, for 

 fntui'e use, the autlmr wouhl be olilige(l f(-)r whatever data the oliservers of trees 

 rnav have and hnd it eonveuieut ti:i send that would lie important to have in 

 this connection. 



The wood-structui'e jiictures i-e]iresent transverse sections (the end view of 

 the grain) magnihe(l unitui-iidy about fifteen diameters. That is a])proxi- 

 matel.y the maguiticatiou seeuri'd by a good simjde magnifier. Such a glass is 

 cput^ essential in ideulifyiug woods, bv comparison, havino; first exposed the 

 end of tlie grain with a sjiarp knife to reveal its structure. 



In rhe foot-notes, following the letter-press on the right-hand page, will Ijc 

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

 adoi)ted ditfer from the names used in this work. " A. AV." indicates 

 AMERT(''AN WOODS, in wliich work the sjiecies is further considered, 

 especiallv wilh refereiiee to its woods, and in which actual s])ecimens of same 

 may be seen. The Uouian numeral indicates the part or \'olumc! in whi(di a 

 species is found and llie Aral)ic numeral its st>rial nundjer. (See pages follow- 

 ing the index at (dose of this volume.) 



[vii] 



