244 



ROSACEAE. 



VOL. II. 



i. Opulaster opulifolius (L.) Kuntze. Ninebark. Fig. 2213. 



Spiraea opulifolia L. Sp. PI. 489. 1753. 



Neillia opulifolia Brew. & Wats. Bot. Cal. i: 171. 



1876. 

 Opulaster opulifolius Kuntze, Rev. Gen. PI. 949. 1891. 



A shrub 3-io high, with recurved branches, 

 glabrous twigs and foliage, the bark peeling off 

 in thin strips. Stipules caducous; leaves peti- 

 oled, ovate-orbicular, obtusely or acutely 3-lobed, 

 cordate, truncate or broadly cuneate at the base, 

 i '-2' long, or larger on the young shoots, the 

 lobes irregularly crenate-dentate ; corymbs ter- 

 minal, peduncled, nearly spherical, many-flowered, 

 i '-2' broad; pedicels slender, glabrous or slightly 

 pubescent, 5 "-8" long ; flowers white or purplish ; 

 calyx glabrous or somewhat pubescent ; follicles 

 3-5, glabrous, shining, 3"-s" long, obliquely 

 subulate-tipped, twice as long as the calyx. 



River-banks and in rocky places, Quebec to Georgia, 

 Tennessee and Michigan. June. 



Opulaster australis Rydb., growing in the moun- 

 tains from Virginia to South Carolina, appears to be a 

 race of this species with smaller follicles. 



2. Opulaster intermedius Rydb. Prairie 

 Nine-bark. Fig. 2214. 



O. intermedius Rydb. in Britton, Man. 492. 1901. 



Physocarpus intermedius C. K. Schneider, Handb. 

 Laubh. i : 807. 1906. 



P. missouriensis Daniels, Univ. Mo. Stud. Sci. i : 291. 

 1907. 



A shrub similar to O. opulifolius in aspect, 

 foliage and inflorescence, the leaves mostly nar- 

 rower, and narrowed at the base. Calyx densely 

 stellate-pubescent; follicles 3 or 4, abruptly acu- 

 minate, 3i"-4" long, permanently stellate-pubes- 

 cent. 



River-banks and rocky woodlands, southern On- 

 tario and western New York to South Dakota, Illi- 

 nois, Missouri, Arkansas and Colorado. 



2. SPIRAEA [Tourn.] L. Sp. PI. 489. 1753. 



Shrubs, with alternate simple pinnate or pinnatifid mainly stipulate leaves. Flowers 

 terminal or axillary, racemose, cymose, corymbose or paniculate, white or pink, perfect. 

 Calyx persistent, its tube mainly campanulate, 4-5-lobed. Petals 4-5, inserted on the calyx, 

 short-clawed. Stamens 20-60, distinct, inserted on the calyx ; filaments filiform ; anthers 

 didymous. Disk adnate to the calyx-tube. Pistils commonly 5 (rarely 1-8), superior, sessile 

 or short-stipitate, alternate with the calxy-lobes. Stigmas capitate or discoid; ovules 2-o. 

 Follicles usually 5, not inflated, dehiscent along i suture. Seeds linear, pendulous, the testa 

 dull; endosperm none. [Greek, twisting, the pods twisted in some species.] 



About 70 species, natives of the north temperate zone. Besides the following, about 12 others 

 occur in the southern and western parts of North America. Type species : Spiraea salicifolia L. 



Flowers in dense terminal panicles. 

 Glabrous or puberulent. 



Leaves broadly obovate ; inflorescence glabrous or nearly so. i. S. latifolia. 



Leaves narrowly oblanceolate or oblong ; inflorescence densely puberulent or tomentulose. 



2. S. alba. 



Twigs and lower surfaces of the leaves woolly-pubescent. 3. S. tomentosa. 



Flowers in terminal corymbs. 

 Calyx glabrous ; native. 



Leaves broadly oval or ovate, thick, serrate. 4. 5". corymbosa. 



Leaves oblong, thin, nearly entire. 5. S. virginiana. 



Calyx pubescent ; introduced. 6. 5". japonica. 



