422 ROSACEAE 



on the stolons. Hypanthium almost flat. Bractlets, sepals, and petals nor- 

 mally 5. Petals yellow, broadly elliptic or almost orbicular, not at all unguicu- 

 late. Stamens 20-25, in three series, inserted as in Potentilla; filaments filiform; 

 anthers didymous, dehiscent by a longitudinal slit. Receptacle hemispheric, 

 bearing very numerous pistils. Styles filiform, lateral, scarcely deciduous. 

 Mature achenes with thick pericarp. Seeds ascending and amphitropous. 



Achenes corky, with a deep groove; stem and petiole and rachis of the leaves densely 



pubescent, with at first ascending and later spreading hairs. 



Leaves silvery on both sides. 1. A. argentea. 



Leaves green and glabrate above. 2. A. Anserina. 



Achenes not corky, without a groove; stem and petiole and the rachis of the leaves gla- 

 brous or slightly appressed-hairy and glabrate; hypanthium acute at the base. 



3. A. subarctica. 



1. A. argentea Rydb. Basal leaves 1-2 dm. long, pinnate, with 11-25 

 larger leaflets and smaller ones interposed; larger leaflets 1-3 cm. long, obovate, 

 rounded at the apex, serrate, white-silky on both sides or slightly greener above; 

 bractlets usually entire, about equalling the ovate or ovate-lanceolate sepals; 

 petals obovate or broadly oval, 6-9 mm. long. Wet places: Mack. S.D. 

 N.M. Ariz. Ore. B.C.' Plain Mont. My-Au. 



2. A. Anserina (L.) Rydb. Leaves 1-2 dm. long, interruptedly pinnate, 

 with 9-31 larger leaflets and smaller ones interposed, spreading or flat on the 

 ground, slightly silky and green above, white-silky and tomentose beneath; 

 larger leaflets 14 cm. long, oblong or oblanceolate, usually acute, deeply and 

 sharply serrate; bractlets simple and lanceolate, or ovate-lanceolate, toothed or 

 divided, generally a little longer than the broadly ovate sepals; petals oval, 7-10 

 mm. long. Wet places: Newf. N.Y. Calif. Alaska; Eurasia. Plain Mont. 

 My-Au. 



3. A. subarctica Rydb. Basal leaves 7-15 cm. long, ascending; rachis 

 silky, with appressed or ascending hairs; larger leaflets 15-19, dark green and 

 sparingly silky above, densely white-silky and tomentose beneath, deeply serrate, 

 the upper leaflet 1.5-2 cm. long; hypanthium about 5 mm. wide, silky and tomen- 

 tulose, acute at the base; bractlets linear-lanceolate, 3-6 mm. long; sepals ovate, 

 5-6 mm. long; petals oval or suborbicular, about 8 mm. long. Wet places: 

 Alaska Yukon Ida. Mont. Mont. Subalp. Je-Au. 



14. COMARUM L. MARSH CINQUEFOIL, PURPLE MARSHLOCKS, 



COWBERRY. 



Aquatic perennials, with long creeping rootstocks and pinnate leaves. Inflor- 

 escence cymose. Hypanthium almost flat or slightly saucer-shaped, enlarging 

 in fruit, more or less tinged with red. Bractlets, sepals, and petals 5. Petals 

 red, ovate, acuminate. Stamens 20-25, inserted near the base of the receptacle; 

 filaments filiform, stout; anthers flat, cordate at the base, attached by the back, 

 and opening by longitudinal marginal slits. Receptacle hemispheric, enlarging 

 in fruit and becoming ellipsoid or hemispheric and spongy. Pistils numerous. 

 Styles lateral, filiform. Seeds amphitropous. 



1. C. palustre L. Stem ascending, 2-5 dm. high, more or less hirsute, with 

 short spreading hairs, somewhat glandular on the upper portion; leaves pinnate, 

 with 5-7 more or less approximate leaflets, green above, paler and purple-veined 

 beneath, sparingly hairy, in age glabrate; leaflets elliptic or oval, mostly 

 acute at both ends, to linear-oblong, 5-8 cm. long and only 1-2 cm. wide, obtuse 

 or rounded at the apex; hypanthium in flower 7-8 mm., in fruit about 15 mm. in 

 diameter, short-pilose and glandular-pubescent; sepals ovate to lanceolate, 

 acuminate, about 1 cm. long in flower and 1.5 cm. in fruit; petals spatulate or 

 ovate, acuminate or acute, scarcely half as long as the sepals. Wet bogs: Greenl. 

 -Lab. N.H. Wyo. Calif. Alaska. Mont. Jl-S. 



15. FRAGARIA L. STRAWBERRY. 



Perennial acaulescent herbs, with scaly rootstock, and producing runners 

 which root and form new plants. Leaves (in all ours) ternate, basal. Hypan- 

 thium almost flat. Bractlets, sepals, and petals normally 5. Petals white, or 



