52 



5. Populus tremuloides Michaux. Quaking Aspen. Plate 19. 

 A straight narrow tree up to 3 dm. in diameter, usually about 1-5 tlm. 

 in diam(>tor; bark usually smooth, <>recnish-white or gray, on older 

 tre(>s l)ecoming rough or fissured, and turnin<j darker; shoots glabrous 

 or with a few hairs, turning reddish-brown the first season, later to 

 a, gray; leaves of sprouts and very small trees usually ovate with a 

 cordate base and two or three times as large as leaves of older trees; 

 matui-e leaves on older trees varialilc, glabrous, the prevailing type has 

 a bluish-green leaf which is widely ovate or nearly orI)icular, 3-7 

 cm. long, tiuncate or slightly rounded at the base, usually abru])tly 

 short-pointed at apex, finely and I'egularl.y serrate, the unusual type 

 of leaf is thinner, yellow-green, ovate, z^ as wide as loirg, rounded 

 or wedge-shaped at base, gradually tajiering to a ])oint at the apex, 

 otheiwise as the prevailing fornr; stamens 6-12; capsules about (5 mm. 

 long, on stalks about 1 mm. long; wood light, soft and weak. 



Distribution. — One of the most widely distributed of North 

 American trees. It ranges from Labrador south to Pennsjdvania, thence 

 southwest to northern Mexico, and then north to northern Alaska. It is 

 found at sea level and at elevations of 10,000 feet. There are records 

 of its occurrence in all parts of Indiana. In all of its Indiana stations 

 it glows only in low ground about lakes, swamps, ponds, low places 

 Ijetween sand dunes, and along streams. In manj' places in the lake 

 region it is found in almost piu'e stands over small areas. 



Remarks. — In Indiana this species is not of sufficent size and 

 abundance to be of much economic importance. 



.JUGLANDACEAE. The W.^lnut Family. 



Trees with large, aromatic, odd pinnate leaves; flowers appearing 

 after the leaves unfold, the staminate in catkins, the jiistillate solitary 

 or in clusters; fruit a nut in a fleshy or hard filirous shell; kernel edible 

 or astringent. 



Pith of twigs chambered; staminate catkins thick, sessile or 

 short stalked; stamen.s S-40, glabrous; nuts witli a networli 

 (if rough projf i-tions 1 .Tuglans. 



l-'ith of twigs not chamlicrcd; staminote catkins slender, long- 

 slalked: stamens ;->-l(), hair\-; nuts inorc oi- less angled but 

 smooth 2 Carya. 



1. JUGLANS. The AValnut.s. 



Trees with funowed bark; pulp surrounding nut continuous, without 

 lines of dehiscence on the surface. 



