AMMIACEAE. 



Vol. II. 



I. Oxypolis filiformis (Walt.) Britton. 

 Oxypolis. Fig. 3130. 



Oenanthe filiformis Walt. Fl. Cai. 113. 1788. 

 Oenanthe teretifolia Muhl. Cat. 31. 1813. 

 Tiedemannia teretifolia DC Mem. Omb. 51. pi. 12. 1829. 

 Oxypolis filiformis Britton, Mem. Torr. Club 5 : 239. 1894. 



Stem hollow, 2°-6° high. Leaves reduced to linear 

 hollow usually jointed acute phyllodia i'-i8' long; 

 involucre of several linear-subulate bracts ; umbels 

 2-4' broad, 6-iS-rayed'; rays slender, i'-2' long; 

 pedicels 2"-4" long; fruit oval, 01 slightly obovate, 

 2"-3" long; oil-tubes large. 



In ponds and swamps, southern Virginia to Florida, 

 west to Louisiana. Aug.-Sept. Plants collected in Dela^ 

 ware, referred to this species, differ in having broadly 

 oval corky-winged fruit, an inconspicuous disk, slender 

 conic stylopodium and smaller oil-tubes. Water-dropwort. 



2. Oxypolis rigidius (L.) Raf. Cow- 

 bane Hemlock or Water Dropwort. 

 Fig. 3131. 



Sium rigidius L. Sp. PI. 251. 1753. 



O. rigida Raf.; Ser. Bull. Bot. 218. 1830. 



O. longifolius Britton, Mem. Torr. Club 5 : 239 



1894. 

 Sium longifoUum Pursh, Fl. Am. Sept. 194. 1814. 



Rather slender, 2°-6° high. Leaves simply 

 pinnate, the lower often 1° long or rnore ; 

 leaflets thick, ovate-lanceolate, lanceolate-linear 

 or oblong, entire, or remotely dentate, iV-Z 

 long, 3"-i2" wide; umbels 2'-4' broad, 7-25- 

 rayed; rays slender, i'-4' long; pedicels 2"-9" 

 long; fruit oval, 2V'-z" long, li"-2" broad; 

 oil-tubes small. 



In swamps, New York to Florida, Minnesota, 

 Missouri and Louisiana. Aug.-Sept. Pig-potato. 



21. ' IMPERATORIA [Tourn.] L. Sp. PL 259. 1753. 



Tall perennial herbs, with large ternately divided or 2-pinnate leaves, sheathing petioles, 

 and compound umbels of white flowers. Calyx-teeth obsolete. Petals ovate, mostly emar- 

 ginate. Fruit much flattened dorsally, broadly oval, to nearly orbicular, cordate at both ends, 

 the lateral ribs broadly winged all around, the intermediate and dorsal ribs slender, wingless; 

 oil-tubes solitary in the intervals and 2 on the commissural side. Styles and conic stylo- 

 podium short. Seed-face flr.t. [Named for its supposed forceful medicinal properties.] 



About 10 species, natives of the Old World, the following typical. 



I. Imperatoria Ostruthium L. Master- 

 wort. Pellitory of Spain. Fig. 3132. 



Imperatoria Ostruthium L. Sp. PI. 259. 1753. 



Glabrous, or sparingly pubescent ; stem stout, 

 hollow, erect, 2°-5° tall. Leaves ternately divided 

 into very broad stalked ovate to obovate seg- 

 ments, which are often 3-parted nearly or quite 

 to the base, sharply and unequally serrate and 

 often incised, the segments of the long-petioled 

 lower leaves often s' broad ; rays of the umbels 

 and pedicels very numerous, slender ; involucre 

 none, or of I or 2 lanceolate bracts ; involucel- 

 bracts few, narrow, deciduous; fruit broadly oval, 

 about 2" long. 



In fields, Pocono plateau of Pennsylvania, and 

 Michigan. Reported from Newfoundlaind. Natu- 

 ralized or adventive from Europe. Broad-leaved 

 hog's-fennel. Felon-grass. Imperial masterwort. Fel- 

 onwort. May-July. 



