ULMUS 



3409 



destructive is the elm leaf-beetle, which destroys the 

 foliage. The canker-worm is also serious; to keep it 

 from doing damage, band the trunks a few feet above 

 the ground with cloth covered with a sticky substance, 

 which prevents the ascent of the wingless female. The 

 trees should be sprayed. A borer, Saperda tridentata, 

 sometimes does considerable damage to the wood. The 

 elms grow best in rich and rather moist soil, and the 

 American elm especially requires such a soil to attain 

 its full beauty, but some species, as U. racemosa and (7. 

 alata, do well in drier situations. Elm trees are not 

 difficult to transplant, and rather large trees may be 

 moved successfully if the work is done carefully. 

 They bear pruning well, but generally do not need 

 much attention of this kind. Propagation is by seeds 

 ripening usually in May or June and sown at once. 

 Most of the seeds will germinate after a few days, but 

 some remain dormant until the following spring. 

 Increased also by layers, which are usually put down 

 in autumn and are fit to be removed in one year. A 

 moist and rather light soil is best for this method. 

 Trees raised from layers are said to bear seed less early 

 and less profusely and are therefore especially recom- 

 mended for street trees, as the foliage of trees that fruit 

 slightly or not at all is larger and more abundant. 

 Dwarf forms of U. foliacea and also U. parvifolia and 

 U. pumila may be raised from greenwood cuttings 

 under glass, the cuttings growing most readily if taken 

 from forced plants. U. campestris, U. foliacea, and some 

 of their varieties are also propagated by suckers. In 

 nurseries most of the varieties are propagated by graft- 

 ing, either by budding in summer or by whip- or splice- 

 grafting in spring outdoors or on potted stock in the 

 greenhouse. U. americana, U. campestris, U. foliacea, 

 and U. glabra are used for stocks. 



IXDEX. 



KEY TO THE SPECIES. 

 A. Blooming in spring, before the hs.: 



calyx not divided below the middle. 

 B. Fls. on slender pedicels, drooping: 



Jr. ciliate. 



c. Fr. glabrous except the ciliate mar- 

 gin: branches not corky: margins 

 of hs. ciliate. 



D. Lrs. widest above the middle, 

 densely pubescent beneath: 



buds elongated, pointed 1. laevis 



DD. LTS. widest about the middle, 

 more or less pubescent beneath: 

 buds ovoid, obtusish or acute. 2. americana 



cc. Fr. pubescent: branches usually 



more or less corky. 

 D. Margin of Its. not ciliate; Its. 

 about S in. long, without 

 axillary tufts beneath: buds 



pubescent 3. racemosa 



DD. Margin of Ivs. minutely ciliate; 

 Its. about 2 in. long, with 

 axillary tufts beneath: buds 



glabrous 4. alata 



BB. Fls. short-pediceUed, in dense clus- 

 ters, not pendulous. 

 c. Buds covered with rusty hairs, 

 obtuse: branchlets scabrous with 

 minute tubercles: ITS. ciliate: fr. 



pubescent in the middle 5. fulva 



cc. Buds pale pubescent or glabrous: 

 branchlets smooth: hs. not cili- 

 ate: fr. glabrous. 

 D. LTS. doubly serrate, unequal at 



the base, -7 in. long. 

 E. Young branchlets pubescent: 



hs. scabrous above. 

 T. Fr. with the seed in the 

 center, about %in. broad: 

 petioles short, about y%in. 

 long. 



G. Mature branchlets red- 

 dish brown, hairy 

 while young: hs. only 

 occasionally S-lobed. . . 6. glabra 

 GG. Mature branchlets pale 

 yellowish or grayish 

 brown, glabrous or 

 nearly so while young: 

 Its. usually S-lobed at 



the apex 7. laciniata 



Fr. Fr. with the seed near the 

 apex, $4in. broad or less: 

 petioles V^-^in. long. 

 G. Lts. broadly oval or 

 orate, 2-3 in. long: 

 branchlets not corky.. . 8. campestris 

 GO. LTS. obovate or elliptic, 

 3-4 in. long: branchlets 

 often with corky wings. 9. japonica 

 EE. Young branchlets glabrous or 

 with few scattered hairs: 

 his. smooth or nearly so 

 above: fr. with the seed above 

 the middle, 

 r. Length of Ivs. 8-5 in.; 



petioles ^i-^iin. long.. . . 10. hollandica 

 FF. Length of Its. 2-3H in.; 



petioles ^-^in. long 11. foliacea 



DD. Lts. simply serrate, nearly 



equal at the base, 1-2 in. long.. 12. pumila 

 AA. Blooming in the axils of this year's Ivs. 

 in summer or autumn: calyx divided 

 below the middle. 



B. Lrs. simply serrate, small: fr. gla- 

 brous 13. parvifolia 



BB. Lrs. doubly serrate: fr. pubescent, 

 c. Racemes 3-6-fld.: Its. 1-2 in. long, 



obtuse or acute 14. crassifolia 



cc. Racemes many-ftd.: hs. 2-S in. 



long, acuminate 15. serotina 



1. Igfevis, Pall. (U. pedunculata, Foug. U. effusa, 

 Willd. U . ciliata, Ehrh. U. racemdsa, Borkh., not 

 Thomas). Tree, attaining 100 ft., with spreading 

 branches, forming a broad open head: branchlets 

 pubescent, usually until the second year: buds glabrous, 

 acute: Ivs. oval or obovate, very unequal at base, acu- 

 minate, sharply doubly serrate, usually glabrous above, 

 pubescent beneath, 2-4 in. long: fls. slender-pedicelled; 

 calyx with 6-8 exserted stamens: fr. ovate, notched, the 

 incision not reaching the nutlet. Cent. Eu. to W. Asia. 

 H.W. 2:39, p. 9. I.T. 6:220. R.F.G. 12:666. 

 Rarely cult., and with less valuable wood. The trunk 

 and the limbs are, as in the American elm, often clothed 

 with short branchlets. 



2. americana, Linn. (U. alba, Raf.). WHITE ELM. 

 WATER ELM. AMERICAN ELM. Figs. 3877, 3878, 3879. 



