Addisonia 11 



(Plate 86) 



LEPADENA MARGINATA 

 Snow-on-the-mountain 



Native oj the central and western United States 

 Family Euphorbia ceae Spurge Family 



Euphorbia niarginata Pursh, Fl. Am. Sept. 607. 1814. 



Euphorbia leucoloma Raf. All. Jour. 177. 1833. 



Lepadena leucoloma Raf. Fl. Tell. 4: 1 14. 1838. 



Dichrophyllum marginatum Klotzsch & Garcke, Monatsber. Akad. Berlin 1859: 



249. 1859. 

 Lepadena marginata Nieuwl. Am. Midland Nat. 2: 300. 1912. 



An annual herb, one to three feet high, with a milky, acrid juice. 

 The stems are erect, green, hairy, and laranched above to form a 

 three-rayed, dichotomous umbel. The leaves are various, sessile, 

 glabrous, ovate or oblong, and entire, except for an occasional lobing 

 of the lower ones. The lower stem-leaves are alternate and scattered, 

 green or somewhat variegated, one to four inches long and about an 

 inch wide, and are usually subtended by narrow, deciduous stipules. 

 A whorl of three or more leaves subtends the inflorescence, and many 

 showy bract-like leaves, bluish-green with wide margins of white, 

 subtend the flower-clusters. On slender hairy peduncles are the 

 campanulate involucres, which are hairy without and within; these 

 have five fimbriate, inconspicuous lobes, attached alternately with 

 which are the glands, usually five in number; these are green, con- 

 cave, peltate, an eighth of an inch in diameter, and have white, 

 petal-like reniform appendages about twice their size. The true 

 flowers, enclosed by the involucre, are a single exserted pistillate one 

 with a three-lobed, three-celled ovary on a long stalk, and three 

 styles, each with two recurved stigmas; this surrounded by numerous 

 staminate flowers with short filaments and yellowish anthers. The 

 calyces are very much reduced. The three-lobed capsules are pilose, 

 one fourth of an inch in diameter; the three carpels separate elastically 

 from a persistent axis, each carpel containing a roundish, pitted, gray 

 seed. 



This spurge was first described by Pursh in 1814, from a specimen 

 in the herbarium of Captain M. Lewis, which had been collected near 

 the Yellowstone River on July 28, 1806, during the return trip of the 

 Lewis and Clarke Expedition. Euphorbia marginata was one of the 

 hundred or more plants described by Pursh from Captain Lewis' 

 collection. Rafinesque, in his Flora Telluriana (1838) gave the name 

 Lepadena to his older Euphorbia leucoloma, and in 1859 our species 

 was designated Dichrophyllum marginatum by Klotzsch and Garcke, 



