[Reprinted from ihe Bullktin op thi; Tokrev Botanilal Cli'B, 19 : December, 1903. | 



Studies in the Asclepiadaceae— VI. Notes on the Genus Rouliniella 



By Anna Murray Vaii. 



A close examination of herbarium specimens variously labelled 

 Roulinia Jacqiiiiiii, R. unifaria and R. raccmosa show that there 

 are several species which if not new are at least deserving of rec- 

 ognition ; and this is an attempt to straighten out some of the 

 species of a most interesting little genus. 



About twenty-one or twenty-two species can be enumerated, 

 ranging from Texas to Argentina ; but as the genus is but poorly 

 represented, even in foreign herbaria, it is difficult withoi^t careful 

 dissection to determine whether all the species credited to Roulinia 

 are correctly placed. 



Rouliniella 



Roulinia Decne.; D. C. Prod. 8: 516. 1844; Schumann, 

 Die nat. Pflanzenfam. 4-: 255. 1895. Not Brongniart, 1840. 



The seven species enumerated here all bear small flowers and 

 are closely related. The available material of the South American 

 species is at present too scanty to study with any kind of satisfac- 

 tion.* 



Ke>- to tlie Species 



Crown-segments not exceeding the stigma. i. R. unifaria. 



Crown-segments barely exceeding the stigma, conspicuously 3-lobed. 



2. R. Coltinibiana. 

 Crown-segments exceeding the stigma, long-ligulate. 

 Flower-buds sub-globose. 



Central lobe of the crown-segments obscurely 3- toothed at the apex ; floweT- 



buds obtuse. 3. R. Palmeri. 



Central lobe of the crown-segments entire ; flower-buds acutish. 



4. R. racemosa. 

 Flower-buds ovate, acute or sub-acuminate. 



Central lobe of the crown -segments truncate at the apex. 5. R. lignosa. 

 Central lobe of the crown-segments acute at the apex. 6. R. foetida. 

 Central lobe of the crown-segments very long and slender, undulate. 



7. R. Jaiiscana. 



*The accompanying figures represent : ^, the bud ; c, the crown (diagrammaticaliy 

 enlarged) ; /, the expanded flower, and are all magnified four diameters ; /, the pollinia, 

 are magnified twenty diameters. 



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