72. POPULUS TEEMULOIDES QUAKING ASP. 39 



GENUS POPULUS, TOURN. 



Leaves broad, more or less heart-shaped or ovate, and petioles which are long and 

 often vertically compressed. Flowers appearing before the leaves in long, drooping, 

 lateral, cylindrical catkins, the scales of which are furnished with a fringed margin; 

 calyx represented by an oblique, cup-shaped disk with entire margin; stamens 8-30 

 or more, with distinct filaments; pistil with very short, bifid style, and large, 2-lobed 

 stigma. Fruit as described for the order. 



Represented by rather large trees. ('A Latin word, meaning the people, and appli- 

 cable either from the fact that these trees are often set along public walks, or in 

 allusion to the tremulous leaves which are in constant agitation like a crowd of 

 people.) 



72. POPULUS TREMULOIDES, MICHX. 

 QUAKING ASP, ASPEN. 



Ger., Amerikanisclie Zitter-Espe; Fr., Le Tremble d'Amerique; Sp., 



Alamo tremblon. 



SPECIFIC CHARACTERS: Leaves ovate-orbicular, with a short, sharp apex, small, 

 the blade being usually not over 2 inches in length and of about equal width; serrate, 

 smooth both sides ; margins pubescent, petioles 2-3 inches long, slender and laterally 

 compressed; branchlets terete. Flowers appear in April (before the leaves) in hairy 

 aments; stamens 6-20; styles 2, bearing 2-3 narrow lobes; scales 3-4-cleft and 

 fringed with long hairs. Fruit small oblong-conical, thin-shelled and 2-valved cap- 

 sules, borne in pendulous ainents; seeds very small. 



( Tremuluides is from the Lat. tremula from tremo, I shake the specific name 

 of a European species, and the Gk., si'doZ, appearance, designating a resemblance to 

 that species.) 



A small tree, rarely attaining 60ft. (18 m.) in height and 2 ft. (0.60 m.) 

 in thickness of trunk, with smooth, pale clay-colored bark, which on old 

 trunks checks into rough, grayish-black ridges. Owing to the laterally 

 compressed nature of the slender petioles, the leaves are in constant agi- 

 tation, moved by the slightest breeze. This is a trait more or less com- 

 mon to all of the Poplars, but in no species is it as well marked as in 

 this. 



HABITAT. This is considered the most widely distributed of North 

 American trees. It is found throughout British America from Labrador 

 and Newfoundland to Alaska, southward into Pennsylvania and Ken- 

 tucky in the east and to central California in the west, and among the 

 mountains to New Mexico and Arizona. 



PHYSICAL PROPERTIES. Wood light, soft, not strong, close-grained, 

 of cottony fiber and soon decaying when in contact with the soil. It is 

 of a light-brown color with thick, nearly white, sap-wood. Specific 

 Gravity, 0.4032; Percentage of Ash, 0.55; Relative Approximate Fuel 

 Value, 0.4010; Coefficient of Elasticity, 81441 ; Modulus of Rupture, 

 t)77 ; Resistance to Longitudinal Pressure, 330; Resistance to Indenta- 

 tion, 80 ; Weight of a Cubic Foot in Pounds, 25.13. 



