270 PROCEEDINGS OP THE AMERICAN ACADEMT 



XV. 



CONTRIBUTIONS TO AMERICAN BOTANY. 



By Asa Gray. 



CommuDicated December 8, 1886. 



1. Revision of some Polypetalous Genera and Orders 

 preciirsori/ to the Flora of North America. 



Papaveracece. 



The following is thought to be a somewhat improved arrangement of 

 the North American genera. 



Tribe I. Platystemone^. Leaves mainly opposite or whorled 

 and entire. Flowers usually trimerous, with a lobed or angled ovary, 

 and a distinct stigma terminating each carpel and so alternate with 

 the placentae. PJatystemon, Platystigma. 



Tribe II. Papavere^. Leaves mainly alternate. Flowers rarely 

 trimerous. Carpels completely combined, even the stigmas confluent 

 or radiate from a common centre, never more numerous than the pla- 

 centae. — I. Petals (4 or 6) usually scarious-marcescent and persistent 

 till the fruit matures : capsule of 3 to 6 valves alternating with as 

 many nerviform placentae. Canhya ; trimerous, and stigmas opposite 

 placentae. Arctomecon ; dimerous, and stigmas alternate with the pla- 

 centae. II. Petals 8-12, not crumpled in bud, which is never droop- 

 ing; deciduous stigmas (2) alternate with the placentre. Sanguinaria. 

 III. Petals 4 or 6, usually crumpled in the bud, deciduous. 1. Shrubby, 

 and with stigmas over the two valves, i. e. alternate with the nerviform 

 placentae. Dendromecon. 2. Shrubby-based, pluricarpellary, and stig- 

 mas over the septiform placentas. Romneya. 3. Herbaceous, and 

 stigmas over the placentae. Argemone, Papaver, Meconopsis, Stylopho- 

 rum, Chelidonium, Glaucium. 



Tribe III. Hdnnemanni^. Leaves alternate. Flowers dimerous, 

 erect in the bud, as if perigynous from dilatation and excavation of the 

 torus. Stigmas twice or thrice as many as the placentae. Capsule 

 siliquiform, pliiricostate, elastically two-valved from base to apex. 

 Hunnemannia, Eschscholtzia. 



