456 WILSON EXPEDITION TO CHINA 



and July 1900 (Veitch Exped. No. 48, type of B. Wilsoniana; 

 flowers and fruits); same locality, April and July 1900 (Veitch Exped. 

 No. 48"*; flowers and fruits); north of Ichang, alt. 700-1700 m.^ 

 woodlands abundant, June 1907 (No. 3371; tree 5-20 m. tall, girth 

 0.3-1.5 m.; fruits); same locality, May 6, 1907 (No. 3371^; flowers; 

 same locality. May 1901 (Veitch Exped. No. 841; flowers); Chienshih, 

 A. Henry (No. 7402; sterile). Eastern Szech'uan : Wushan Hsien,, 

 A. Henry (No. 5667; fruits); " Heoupin prope Tchen-keoii," alt. 

 1400 m,, P. Farges (No. 1010; type of var. pyrifoUa, ex Franchet) ; 

 same locality, P. Farges (without No.; type of B. tuminifera, ex 

 Winkler). Western Szech'uan: Wa-shan, alt. 1300-2000 m., 

 woods, June 1908 (No. 816 and 3368; tree 10-17 m. tall, girth 0.9-1.8 

 m.; fruit); Mupin, alt. 1700-2000 m., woods, July 1908 (No. 915 and 

 3367; tree 5-13 m. tall, girth 0.45-1.5 m.; fruits); Yung4iing Hsien„ 

 ascent of Ta-hsiang-ling, alt. 1000-1300 m.; June 1907 (No. 3364; thin 

 tree, 3-8 m. tall; fruits); east of Mao-chou, alt. 1300-2300 m., thickets, 

 May 23, 1908 (No. 3366; tree 7-13 m. taU, girth 0,6-1.8 m.; young 

 fruits); Mt. Omei, June 1904 (Veitch Exped. No. 5792; tree 8 m. 

 tall; fruits); same locality, 1200 m., E. Faber (No. 212; fruits); 

 Nanch'uan, A. von Rosthorn (No. 1533 ?, No. 1534; type of var. 

 resinosa, ex Dieb). 



This species is a rather variable one. As long as we compare only the types of 

 the different forms mentioned above they may appear distinct species or well char- 

 acterized varieties. But with a careful study of all the specimens before me 1 find 

 it impossible to limit even good varieties. The shape of the leaves and bracts, the 

 pubescence of the different parts and the length of the fruiting catkins are extremely 

 variable. The tj^pe of B. luminifera Winkler has broad-ovate and often slightly 

 cordate leaves and does not have the same kind of tomentose pubescence or the 

 very long catkins which 1 considered the principal characters of B. Wilsoniana 

 Schneider. On the other hand, B. hupehensis Sclmeider represents a more glabrous 

 form with short catkins. But the length of the catkins is the same in forms which 

 differ in pubescence and in tlie shape of the leaves. The glands of the under surface 

 of the leaves do not afford any sufficient character to distinguish forms. Geograph- 

 ically the species seems to be well separated from B. alnoides Hamilton, which is a 

 much more subtropical species and may be easily distinguished by the fruiting cat- 

 kins being more than one and by the shape, texture and serration of the leaves. 



This is the low-level Birch of western Hupeh and of Szech'uan. In Hupeh and 

 eastern Szech'uan it grows between 500 and 2000 m. of altitude and in western Sze- 

 ch'uan between 1000 and 2500 m. Though very abundant it does not form pure 

 woods, but is always associated with other trees. It rarely exceeds 20 m. in height, 

 has rather slender branches and a trunk from 1 to 2.5 m. in girth. The bark is firm 

 and smooth and dark-colored on young trees, becoming dull yellowish gray or even 

 dull reddish brown on old trees. It does not exfoliate. 



Pictures of this tree will be found under Nos. 163, 517, 556, 565 of the collection 

 of my photographs and also in my Vegetation of Western China, Nos. 135, 136, 137, 

 138. E. H. W. 



