99 



Octol:ier. The species that mature their fruit the first year are popu- 

 larly and commercially classed as "white oaks." Those that mature 

 their fruit the second year are classed as "red, black oi- bristle-tipped 

 oaks." 



The oaks are the largest genus of Indiana trees, and commercially 

 are the most important of all trees of the State. Thejr are the longest 

 lived of all the trees that occur in the State, and while they have 

 numerous insect enemies none of them prove fatal to it, except a certain 

 gall insect. 



Note: — In collecting leaf specimens of oaks for identification it 

 should be borne in mind that the foliage is quite variable. The leaves 

 of seedlings, coppice shoots and of vigorous shoots of old trees some- 

 times vary considerably in size, form and leaf-margins. Also leaves of 

 old trees that grow m the shade usually have the margins more nearly 

 entire than the tyjiical leaves. For example leaves may be found on 

 the lower and interior branches of a pin oak which are not lolied to 

 beyond the middle, which throws them into the red oak group. 



Bark gray, (except in No. .5) more or less .sealy; mature leaves 

 ne\-er \\ith tiristle tips; fruit maturing the first year. 



Mature leaves smooth beneath 1 Q. alba. 



Mature leaves pubescent beneath. 



Primary ^•eins beneath sho^\' regular pinnate venation. 



Some of the primary veins beneath end in a sinus 2 (^. bieolor. 



All primary veins beneath end in teeth of the margin.. . 



Tips of leaves of fruiting branches sharp-pointed, 



usually forming an acute angle; fruit sessile or 



nearly so 3 Q. Muhlenbergii 



Tips o{ lea^'es of fruiting Itranches rounded or if 



sharp-pointed, it rarely forms an acute angle; 



fruit peduncled. 



Petioles green and woolly pubescent beneath 



(rarely almost glabrous); under surface of 



leaves veh'ety to the touch; bark gray, scaly, 



of the white oak type; trees of low ground. . . 4 Q. Miehau.xii. 



Petioles yellowish and smooth beneath, or rarely 



somewhat pubescent; imder surface of leaves 



leaves not velvety to the touch ; bark dark, and 



tight, of the red oak type; trees of high ground 



(in Indiana confined to the "knobstone" 



area) 5 Q. Prinus. 



I'rimary ^"eins beneath show irregular venation. 



Last year's growth pubescent; acorns generally less 



than 12 mm. in diameter 6 Q. stellata. 



Last year's growth glabrous or nearly so; acorns mcxre 

 than 12 mm. in diameter. 



