149. Agrostis nebulosa. 



(XX) 



AGROSTIS 



BB. Palea wanting. 

 canina, Linn. RHODE ISLAND BENT. BROWN BENT. 



Slender, erect, cespitose, Yy-fi ft.: spikelets 1 line long; 



lemma bearing about the middle an exserted bent awn. 



Dept. of Agric. B.P.I. Bull. 68, pi. 9. Eu. Cult, as a lawn 



grass, and sparingly escaped. Much of the commercial 

 seed under this name is Agrostis 

 alba var. vulgaris. The seed of 

 A. canina may be distinguished 

 by the absence of the palea. 



AA. Panicle diffuse, the main 

 branches scabrous, long and 

 hair-like, naked below. 

 B. Plants annual: palea 



present. 



nebulosa, Boiss. & Reut. 

 CLOUD-GRASS. Fig. 149. Culms 

 branched below, slender, 1 ft.; 

 blades few and small; ligule 2-3 

 lines; panicles oblong, about half 

 the plant, delicate, the branches 

 verticillate; spikelets J^line, long- 

 pedicelled. sometimes awned. 

 Spain. Cult, for dry bouquets. 

 Sometimes called A. capillaris 

 but is not A. capillaris of botani- 

 cal authors. 



BB. Plants perennial: palea 



wanting. 



hiemalis, B. S. P. (A. scabra, 

 Willd.). HAIR-GRASS. TICKLE- 

 GRASS. SILK-GRASS. Culms low 

 and delicate, 1-2 ft.; blades 

 small and mostly radical; pani- 

 cles very diffuse, the spikelets borne toward the ex- 

 tremities of the branches. Dept. of Agric. B.P.I. Bull. 

 68, pi. 26. The panicles break away at maturity and 

 are blown about by the wind. The young panicles are 

 often used for dry bouquets. 



A. minittiflbra. See Sporobolus minutiflorus. 



A. S. HITCHCOCK. 



AGUACATE, ALLIGATOR PEAR, AVOCADO: Persea. 



AILANTHUS (from its native name Ailanto, meaning 

 Tree of Heaven). Syn., Pongelion. Simarubdcese. 

 Trees chiefly grown for their handsome large foliage. 



Large trees: Ivs. alternate, odd-pinnate, deciduous: 

 fls. small, in large terminal panicles, 

 polygamous; sepals and petals 5 or 6; 

 disk small, 10-lobed; stamens 10; carpels 

 5 or 6: fr. consisting of 1-5 distinct oblong 

 samaras with the compressed seed in the 

 middle. Eight or 9 species in Cent, and 

 S. Asia and in N. Austral. 



These trees are sparingly branched, with 

 large pinnate foliage, inconspicuous green- 

 ish flowers in upright panicles followed by 

 winged fruits; the foliage exhales a dis- 

 agreeable odor when bruised. The ailan- 

 thus foliage gives a tropical effect when 

 the growth is very strong. 



The Chinese species are fairly hardy North; only as 

 young plants are they somewhat tender. They are 

 very rapid growers and stand smoke and dust well. If 



Clants are cut back to the ground after they have 

 ecome established (in two or three years after plant- 

 ing), they will throw up very strong shoots and make an 

 excellent screen. This practice may be repeated year 

 after year. Sumacs, paulownias, basswoods, mulber- 

 ries, and other fast-growing things may be treated in 

 this way. The ailanthus foliage is very like that of the 

 cedrela (which see for illustration of differences). The 

 best known is A . altlssima, which is often planted as 

 a street tree, particularly in cities, as it resists smoke 



16 



AILANTHUS 



241 



better than many other trees and is not attacked by 

 insects. For street planting, the fertile plant only 

 should be used, because the male exhales a disagreeable 

 odor when flowering, and the pollen is said to cause 

 catarrhal troubles. It grows in almost any soil, but 

 best in a light and somewhat moist one. 



Propagation is by seeds which must be sown soon 

 after ripening, and by root-cuttings. It suckers from the 

 roots. 



A. Branchlets and petioles glabrous or only finely pubes- 

 cent: Ifts. glabrous beneath. 



altissima, Swingle (A. glanduldsa, Desf.). TREE OF 

 HEAVEN. Fig. 150. Tree, to 60 ft.: young branchlets 

 minutely pubescent, usually dull yellowish brown: Ivs. 

 VA-2 ft. long; Ifts. 13-25, stalked, ovate-lanceolate, 

 usually truncate at the base, 3-5 in. long, finely ciliate, 

 with 8-10 pairs of veins, glabrous and glaucescent 

 beneath, near the base with 2-4 coarse teeth, each with 

 a large gland beneath: samaras 1 Ji in. long. June, July. 

 China. G.C. III. 2:365. Gn. 24, pp. 63,65 (habit); 32, p. 

 330. Mn. 10, p. 152 (habit). M.D.G. 1901:324 (habit). 

 Var. erythrocarpa, Rehd. (A. erythrocdrpa, Carr. A. 

 rubra, Hort.). Lvs. darker green above and more 

 glaucous beneath: fr. bright red, very effective in late 

 summer and autumn. Var. pendulifolia, Rehd. Lvs. 

 very large, drooping. R.H. 1906, p. 545. Var. sutch- 

 uenensis, : Rehd. & Wilson (A. sutchuenensis, Dode). 

 Young branchlets reddish brown, glabrous, lustrous: 

 petioles purplish glabrous: Ifts. not ciliate, cuneate at 

 the base, at least in older plants: fr. about 2 in. long. 

 \V. China. In China this species and A. Vilmoriniana 

 are sometimes planted as the host of a silkworm, Attacus 

 cynthia, which produces a coarse silk, inferior to that 

 of the common silkworm. As a shade and street tree, it 

 is now much planted in temperate regions and natural- 

 ized in some localities. 



Giraldii, Dode. Tree; young branchlets finely pubes- 

 cent; petioles purplish: Ivs. 2-3 ft. long; Ifts. 33-41, 

 closely set, lanceolate, 4-6 in. long, with 2-4 glandular 



teeth near the base, undulate at the margin and long- 

 pointed, with 14-15 pairs of secondary veins, dark 

 green above, pale green beneath: panicle 8-12 in. long: 

 fr. 2 1 A in. long. W. China. 

 AA. Branchlets and petioles, at least in young trees, 



prickly and pubescent: Ifts. pubescent beneath. 

 Vilmoriniana, Dode (Pongelion Vilmorinianum, Van 

 Tieghem. A. altlssima var. spindsa, Bois). Tree, to 

 60 ft.: Ivs. 2-3 ft. long; Ifts. 17-35, oblong-lanceolate, 



