12 



DE. E. E. GATES— CONTEIBUTION TO A 



Key to Oenotliera species of the Onagra group 



* 



Petals cruciate, narrow and linear. 



Cruciate varieties of 0, Lamarckiana and 0. biennis are described in DeVries, 



( 



Die Mutationstlieorie/ ii. pp. 593-633. 



Petals broad ; flowers large (petals 30-60 mm. long). 



Style short, so that the stamens surround the stigma in the butl ; flowers about 



7 cm. in diameter, petals 4 cm. long ^- Simsiana 



Style long, so that the flowers are not self-pollinated in the hud. 



Stems decumbent ; plants clothed with soft pubescence, or canescently. 



• 



strigose. 



Leaves ovate-elliptical or oblong, rather obtuse 0. Drummondii. 



Leaves oblong-lanceolate, repandly denticulate, acute 0. Jamesii. 



Stems erect, more or less muricated ; flower-buds nearly or quite glabrous, 



bearing few or no long muricate hairs. Leaves usually more or less 



ciliate and pubescent. 

 Eosette-leaves narrowly oblanceolate, tapering above the acute apex. 



Stem-leaves smaller, passing into sessile bracts 0. MacBridea. 



Rosette-leaves spatulate-lanceolate with long petioles. Stem-leaves 



subsessile, oblong-lanceolate 0. macrosceUs. 



Eosette-leaves oblong-spatulate, tapering at the irregularly pinnatifid- 



toothed base into a long, broad petiole. Stem-leaves ovate-lanceolate, 

 tapering at both ends, denticulate, blade passing below into a short, 



margined petiole 0. grandijiora. 



Eosettc-leaves broadly linear to linear-spatulate, sinuate. Stem-leaves 



undulate or repand-denticulate, linear to linear-oblong 0. argillicola. 



Stems erect, muricated. Flowers not glabrous, but rather densely covered 



with muricated hairs. 

 Leaves canescently pubescent, plane, rather narrowly lanceolate, sessile, 



ob>curely denticulate 0. Hookeri. 



Leaves and usually buds less pubescent (fewer muricated hairs) . . , , 0. Lamarckiana and 

 Petals broad ; flowers smaller (petals about 12-30 mm. long). [its segregates. 



Stvle exceeding tlie stamens. Leaves narrowly oblong-lanceolate to linear- 



o 



0. Oakesiana. 



lanceolate. Calyx densely white hirsute-pubescent 0. ornata. 



Style short, not reaching beyond the anthers in the bud. 



Sepal tips spreading ; rosette-leaves narrowly lanceolate, approximately 

 toothed at the acute apex, more deeply toothed at the slender, 



tapering base. Sieds large 



Sepal tips appressed ; plant annual, vvith evanescent rosette of a few small, 



red-spotted leaves, closely resembling 0. grandijiora. Stem-leaves 



lanceolate, remotely denticulate, acute at both ends O. Tracyi. 



Sepal tips appressed ; jlant bieunial. Lower stem-leaves 15-20 cm. long, 



elUptic-oblanceolatc to elliptic-lanceolate, shallowly toothed, and often 

 jagged-tooihed near base, acuminate. Free sepal tips about 2 mm. 

 long O. biennis. 



^M 



• I am indebted to Sir David Train, F.E.S., Director of the Eoyal Botanic Gardens, Kew, for permission to 

 examine the list of Oenothera species in the next (unpublished) supplement to the ' Index Keweusis/ 



