PLATANACKa:. 



SILVA OF NORTH AMERICA, 



99 



PLATANUS. 



Flowers monoecious, in dense unisexual heads ; sepals 3 to 6, imbricated in 

 aestivation ; petals and stamens as many as the sepals ; disk ; ovary superior, 1 -celled ; 

 ovule usually solitary, suspended. Fruit an akene. Leaves alternate, stipulate, 

 deciduous. 



Platanus, Linnaeus, Gen. 358 (1737); ed. 2, 462. — Adan- 

 son, Fam. PL ii. 377. — A. L. de Jussieu, Gen. 410. — 



Hist. PL iii. 462. 



Bentham & Hooker Gen. iii. 396. 

 Prantl Pflanzenfam. iii. pt. ii. 14 



Endlicher, Gen. 289. — Meisner 



347. 



Baillon, 



Trees, with watery juice, thick deeply furrowed scaly hark exfoliating from the branches and young 

 trunks in large thin plates, terete zigzag pithy branchlets, infrapetiolar buds, and fibrous roots. Buds 

 axillary,^ conical, large, smooth and lustrous, nearly surrounded at the base by the narrow leaf-scars, in 

 which appear a row of conspicuous dark fibro-vascular bundle-scars ; covered by three deciduous scales, 

 the two inner accrescent, strap-shaped, rounded at the apex at maturity and marking in falling the base 

 of the branch with narrow ring-like scars ; the outer scale surrounding the bud and splitting longitudi- 

 nally with its expansion, the second light green, covered with a gummy fragrant secretion, and usually 



Leaves longitudinally plicate 

 in vernation, alternate, broadly ovate, cordate, truncate, or wedge-shaped and decurrent on the petiole 

 at the base, more or less acutely three to seven-lobed, and occasionally furnished with a more or less 

 enlarged basal lobe,^ the lobes entire, dentate with remote minute callous teeth, or coarsely and 

 remotely sinuate-toothed, palmately nerved, penniveined, the veins arcuate and united near the margins 

 and connected by inconspicuous reticulate veinlets, clothed while young, like the petioles, stipules. 



inclosing a bud in its axil,^ the third coated with long rufous hairs. 



an 



d 



young 



branches, with caducous stellate sharp-pointed branching hairs,^ pale on the 



lo 



wer 



and 



rufous on the upper surface of the blade, long-petiolate, the petioles abruptly enlarged at the base and 

 inclosing the buds, turning brown and withering in the autumn before falling ; stipules membranaceous, 

 laterally united below into a short tube surrounding the branch above the insertion of their leaf, acute 

 and more or less free above, dentate or entire, thin and scarious on flowering shoots, broad and leaf- 

 like on vigorous sterile branches, caducous, marking the branch in falling with narrow ring-like scars. 

 Flowers minute, appearing with the unfolding of the leaves, in dense unisexual pedunculate soHtary 

 or spicate heads, the staminate and pistillate heads on separate peduncles or rarely united on the same 



1 The end of the branch of Platanus withers and falls at mid- logic History of the Genus Platanus'] ; American Naturalist, 1878, 



summer with or before the stipiiles of the upper leaf by which it is t. 28 \_Origin of the Plane-treeJ) , who regards them as evidences of 



nearly inclosed, leaving, close to the upper axillary bud which the the descent of our existing American Plane-trees from extinct 



following spring prolongs the branch, an elevated orbicular dark ancestral types, as traces of the leaves of these with well developed 



Act. Nat. Cur. basal lobes have been found in the rocks of the Laramie Group in 



xxii 



irs (Henry, Nov. Act. Nat. Cur. 



Foerste, BulL Torrey Bot. Club, the northern Rocky Mountain region, 



XX. 163, t. 147, f. 9). 



* The peculiar hairs in the thick coat of tomentum which covers 

 the young leaves and shoots of Platanus, and which, easily de- 

 8 The basal lobes, which vary greatly in size and shape, usually tached by the wind, often floats in large flakes through the air in 



2 Hitchcock, Trans. St. Louis Acad, vi, 138, 



occur only on large leaves produced on vigorous shoots from the 



figured 



stumps of trees that have been cut down. 



figured 



447 



Nat 



,mm 



