POL YG ON A CEA E. 351 



i. MACOUNASTRUM Small. 



Low glabrous annual herbs, with fibrous roots, erect or spreading simple or 

 forked stems, alternate or opposite leaves, funnelform membranous ocreae, and 

 minute perfect terminal clustered flowers, subtended by a several-leaved involucre. 

 Calyx 2-4-parted (usually 3-parted), greenish-white, the segments valvate, equal ; 

 pedicels subtended by transparent bracts; stamens 2 or 4, alternate with and often 

 protruding between the calyx-segments; filaments stout; style 2-3-parted; stigmas 

 capitate; achene ovoid, exceeding the persistent calyx; embryo eccentric, accum- 

 bent. Two or three species, the following circumboreal, the others of the higher 

 Himalayas. 



i. Macounastrum Islandicum (L.) Small. Macounastrum. (I. F. f. 1285.) 

 Stems very slender, 2.5-10 cm. long, sometimes tufted. Leaves obovate, oblong 

 or almost orbicular. 2-10 mm. long, fleshy, obtuse, sessile or short-petioled; ocreae 

 about 1 mm. long; involucre consisting of 3-6 obovate or orbicular bracts; flowers 

 fascicled in the involucres, short-pedicelled; calyx 1 mm. long, the segments ovate- 

 lanceolate, rather obtuse; style-branches short; achene less than 2 mm. long, 

 brown, striate, its faces convex. Greenland and Labrador to Hudson Bay and 

 Alaska. Also in arctic Europe and Asia. Summer. 



2. ERIOGONUM Michx. 



Annual or perennial acaulescent or leafy-stemmed herbs, some species very 

 woody at the base, often with tufted stems, and entire alternate opposite or whorled 

 leaves. Flowers small, fascicled, cymose, umbellate or capitate, subtended by 

 5-8-toothed or cleft involucres. Calyx 6-cleft or 6-parted, usually colored, the 

 segments equal or the outer ones larger. Stamens 9 ; filaments filiform, often 

 villous. Style 3-parted; stigmas capitate. Achene pyramidal, 3-angled, more or 

 less swollen near the base, invested by the calyx-segments, or winged. Embryo 

 axial or somewhat eccentric. [Greek, referring to the woolly and jointed stems.] 

 About 160 species, natives of America, mostly of the western U. S. 



Achenes 3-winged. 1. E. alatum. 



Achenes merely angled, never winged. 



Calyx contracted into a stipe-like base. 



Caulescent ; stems topped by compound cymes. 



Stem leaves alternate. 2. E. longifolium. 



Stem leaves opposite or whorled. 



Calyx yellow ; basal leaves rounded at fhe base ; Alleghenian. 



3. E. Allenii. 

 Calyx white or pink ; basal leaves narrowed at the base ; campestrian. 



4. E. Jamesii. 

 Scapose : stems topped by simple umbels. 5. E.flavum. 



Calyx jointed to the pedicel without a stipe-like base. 

 Scapes or peduncles topped by capitate clusters. 



Calyx glabrous ; achenes over 2 mm. long. 6. E. pauciflorutn. 



Calyx villous ; achenes less than 2 mm. long. 7. E. multiceps. 



Scapes or peduncles topped by more or less compound cymes. 

 Involucres erect or at least never drooping. 



Ovaries and achenes completely clothed with wool ; leaf-blades silky 



above with silvery hairs. 8. E. lacfinogynum. 



Ovaries and achenes glabrous or villous at the top ; leaf-blades more or 

 less floccose. 

 Annual ; herbaceous throughout and usually simple at the base. 



9. E. annuum. 

 Perennial ; shrubby and much branched at the base. 



Calyx yellow. 10. E. cantpanulatum. 



Calyx white, pink or reddish. 



Leaf-blades copiously pubescent on both sides. 



11. E. corymbosum. 

 Leaf-blades densely pubescent beneath, inconspicuously so 



above. 

 Inflorescence 2-3 times compound ; branches spreading. 



12. E. microthecum. 

 Inflorescence 5-7 times compound ; branches erect or 



nearly so. 13. E. effusiim. 



Involucres on drooping on deflexed peduncles. 14. E. cernuum. 



