192 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



3. Xanthoxalis stricta (L.) Small. 



Fields or woods; common. May-Aug. Widely distributed in N. Amer. (Oxalis 

 stricta L.; 0. corniculata stricta Sav.) 



4. Xanthoxalis corniculata (L.) Small. 



Waste ground, Washington; rare. June-Sept, Native of tropical regions gener- 

 ally; adventive in the eastern U. S. (Oxalis corniculata L.; 0. repens of Gray's 

 Manual.) 



5. Xanthoxalis filipes Small. 



Woods; common. May-Aug. Md.toGa. (Oxalis filipes Small.) 



86. LINACEAE. Flax Family. 



1. LINUM L. Flax. 



Linum usitatissimum L., cultivated flax, with blue flowers, is sometimes found in 

 waste ground. 



Leaves mostly opposite; stems si rial e-angled; plants of wet soil. Capsules depressed. 



1. L. striatum. 

 Leaves all, except the very lowest, alternate; stems not angled; plants mostly of dry 

 soil. 



Capsules pointed at the top, as long as broad 2. L. floridanum. 



Capsules depressed, flat or broadly rounded at the top, broader than long. 

 Flowering branches erect, rigid; leaves narrowly lanceolate, dull or pale green; 



sepals in fruit usually with numerous glandular teeth 3. L. medium. 



Flowering branches ascending or spreading, flexuous; leaves oblong, deep green; 

 sepals in fruit usually without teeth 4. L. virginianum. 



1. Linum striatum Wall . 



Swamps or low ground; frequenl. July-Sept. Eastern IT. S. (Cathartolinum 

 striatum Small.) 



2. Linum floridanum (Planch.) Trel. 



Dry soil; occasional. July-Sept. Eastern U. S. (Cathartolinum floridanum 

 Small; L. virginianum of Ward's Flora, in part.) 



3. Linum medium (Planch.) Britton. 



Dry soil; frequent. June-Aug. Eastern U. S. (L. virginianum of Ward's Flora, 

 in part; Cathartolinum medium Small.) 



4. Linum virginianum L. 



Dry or moist woods; Rock Creek Park, Paint Branch, and along the Patuxent near 

 Laurel. June-July. Eastern U. S. ( Cathartolinum virginianum Reichenb.) 



A specimen of Kallstroemia parvijlora Norton, of the family Zygophyllaceac, was 

 collected in the Department of Agriculture Grounds in 1895 (G. H. Hicks). Native 

 of the southwestern U. S. 



87. RUTACEAE. Rue Family. 



Zanthoxylum americanum Mill., prickly ash, was reported by Ward from Pierce's 

 Mill, but doubtless only as an escape from cultivation; native of the eastern U. S. 

 A plant of Rida graveolens L., rue, was found in Potomac Park in 1902 (G. IT. Shull); 

 native of Eur. 



1. PTELEA L. 



1. Ptelea trifoliata L. Hop tree. 



Woods along the Potomac; frequent. May-June. Eastern V. S. 

 Known also as wafer asb . 



