RUSTS 



RYXCHOSPORA 



30il 



of wild hosts and of diseased portions of plants is a partly successful 

 method of control. 



Pueeinia chrysanthani. the chrysanthemum rust, is known in the 

 United States chiefly in the uredoepore stage on chrysanthemums 

 of which only some varieties appear to be susceptible. The rust 

 rarely produces serious damage, and is readily controlled by the 

 elimination of susceptible varieties. 



Gymnotporangium juniperi-rirginianae, cedar rust, apple rust. 

 The telia] stage produces the galls known as cedar apples on the red 

 cedar. After rams in spring the teleutospores ooze out from the 

 galls in the form of horn-like gelatinous masses, an inch or more in 

 length. They germinate in place and the sporidia infect the leaves 

 and fruits of the apple on which the aecidial stage is produced. No 

 appreciable damage is caused to the cedar, but apple trees are some- 

 times defoliated by this rust and the damage to orchards is often 

 extensive where cedar trees are abundant. Removal of cedar trees 

 prevents the occurrence of this rust on the apple. The fungus can 

 be controlled also by spraying with bordeaux mixture. 



Gymnosporanffium globosum, another species much like the fore- 

 going, is the common cause of apple rust in the East. 



Cronartium ribicola has uredospores and teleutospores on various 

 species of currants, but is chiefly of importance on account of the 

 destructiveness of its secidial stage to the white pine and other five- 

 leaved pines. Introduced from Europe probably about 1906. Local 

 in northeastern United States at present. 



Coleosporium solidaffinis_ occurs on aster, solidago, and other 

 Composite. It is chiefly of interest because it also attacks the culti- 

 vated aster (Callistephus hortensii) causing considerable damage. 

 The secidial stage occurs on pines. The intervention of this stage is, 

 however, not essential for the maintenance of the fungus since the 

 uredo sori persist through the winter on the rosette leaves of solidago 

 and other Composite. 



Melampsora tremvls is the common orange rust of poplars in the 

 United States. Several races exist which have secidia on larix. pine, 

 and other plants. Numerous other species or subspecies of Meiam- 

 psora occur on willows. The injury caused by these is not great. 



Gymnoconia interstitialis, of the blackberry, has but one spore 

 form, the secidiospores which germinate like teleutospores. The 

 rust is exceedingly common on the blackberry and raspberry 

 covering the whole under surface of the leaves with blisters which 

 burst and display the brilliant orange spore-powder. The mycelium 

 is perennial and permeates the entire host. No satisfactory remedy 

 has been suggested. 



I'redo fici, an unattached uredo-form which is common on fig 

 trees, causing a rusty brown appearance and premature falling of 

 the leaves. Where figs are grown for fruit, considerable damage 

 results to the crop from the loss of leaves. Common also in the 



HEIXRICH HASSELBRIXG. 



RUTA (classical name of rue). Rutace^e. Perennial, 

 glandular, punctate herbs, hardy or half-hardy North, 

 quite hardy South but of no great horticultural value. 



Plants often woody at the base, with terete branched 



ivs. alternate, simple, 3-foliate, pinnately cut or 



compound: fls. in leafy-bracted terminal corymbs or 



panicles, numerous, yellow or greenish; calyx short, 



persistent, 4-5-lobed or parted; petals 4-5, limb arched, 



often dentate or cilia te; stamens 8-10; ovary sessile: 

 caps. 4-5-lobed, the lobes indehiscent or dehiscent at 

 the apex. About 40 species mostly in the Medit. 

 region and a few in W. and Cent. Asia. 



graveolens, Linn- RUE. HERB OF GRACE. Fig. 

 3515. A hardy perennial, woody at the base, lJ^-2 ft. 

 high: Ivs. fragrant, much divided; lobes oblong, the 

 terminal obovate: fls. yellow. July. Prop, by division 

 and seeds. An old medicinal plant, with a very strong 

 aromatic odor; sometimes spontaneous in this country. 



Patavina, Linn. (Haplophyttum Patavium, Hort.). A 

 hardy perennial herb 4-6 in. high: Ivs. glabrous, the 

 lower oblong-spatulate, narrowed at the base, the others 

 trisected and laciniate: corymb dense; pedicels some- 

 what longer than the fls.; fls. golden yellow. June, July. 



F. W. BARCLAY. 

 F. TRACY HtjBBARD.t 



RUTABAGA: Bmssica. 



RYE: Secaif. R., Wild: Elymus. 



RYNCHOSPORA (Greek, snout and seed, alluding to 

 the beaked achene). Also spelled Rhynchospora. 

 Cyperaceae. Chiefly perennials, with more or less trian- 

 gular and leafy culms; suitable for bog or lowland 

 planting, but rare in cultivation. 



Inflorescence terminal or axillary: spikelets panicled 

 or variously clustered, ovate, globular or spindle- 

 shaped; scales open or barely concave; perianth of 

 bristles; stamens mostly 3: achene lenticular, globular 

 or flat, crowned with a conspicuous tubercle or beak. 

 About 300 species, distributed in the tropical and sub- 

 tropical regions, many in Temp. N. Amer. and a few in 

 Temp. Eu. and Asia. 



alba, Vahl. Culm slender, about 6-24 in. high, tri- 

 angular above : Ivs. narrowly linear, almost bristle-form : 

 spikelets lanceolate, white or whitish, densely crowded 

 into a head-like terminal corymb. Bogs, Newfoundland 

 to Alaska southward to Fla., Ky., the Great Lake 

 region and N. Calif., also in Eurasia and Porto Rico. 



fusca, Ait. f. Loosely stoloniferous, culm 8-24 in. 

 high: Ivs. bristle-form: spikelets ovoid-fusiform, chest- 

 nut-color, clustered in 1-4 loose heads, overtopped by 

 the slender bracts. Boggy places, Newfoundland to 

 Ont., southward to Del. and Mich., also in Eu. 



F. TRACY HUBBARD. 



3515. Ruta graveolens. (Flower slightly enlarged.) 



