438 CONTEIBUTIONS FROM THE NATIONAL HERBARIUM. 



27. CmSIUM Hill. Thistle. 



Coarse biennials or perennials; leaves alternate, toothed or lobed, very spiny; 

 heads large, without rays, the bracts tipped with spines; pappus of hairy bristles. 



Leaves closely white-woolly on both sides 1. C. undulatum. 



Leaves green, or woolly only on the under side. 



Stems winged; upper surface of the leaf covered with small appressed spines. 



2. C. lanceolatum. 

 Stems not winged; upper surface of the leaf not spiny. 



Bracts with loose cobwebby hairs; leaves woolly on the under side. 



3. C. hookerianum. 

 Bracts not hairy; leaves glabrous or nearly so 4. C. arvense. 



1. Cirsium undulatum (Nutt.) Spreng. Prairie thistle. Dry shale slopes at 

 east entrance. B. C. to Ariz, and Mich. — Plants 30 to 60 cm. high; leaves with 

 short broad lobes; heads few, 3 to 4 cm. high; bracts with stout spiny tips, not woolly; 

 flowers rose-purple. 



2. Cirsium lanceolatum (L.) Hill. Common thistle. Infrequent on the east 

 slope, but common on the west slope, in woods or fields or on open hillsides. Native 

 of Eur. ; widely naturalized in N . Amer.- — Plants about a meter high, green, the stems 

 with spine-toothed wings; leaves deeply lobed, extremely spiny, thinly woolly 

 beneath; heads usually numerous, 4 to 5 cm. high, the bracts with slender sharp 

 spines ; flowers rose-purple . 



A few plants with white flowers were found. It is very unfortunate that this 

 noxious weed has become so abundant on the west slope; it grows everywhere at low 

 altitudes through the woods and well up along the trails. At Belton it forms almost 

 impenetrable tangles of considerable extent. On the east slope it is still rare, but it 

 is likely to become abundant. 



3. Cirsium hookerianum Nutt. White thistle. Common, especially on the 

 east slope, at low and middle altitudes, in woods or on open slopes; occasionally in 

 meadows above timber line. B. C, Alta., and Mont. — Plants 0.3 to 1 meter high, 

 green; leaves obloug-oblanceolate, lobed or often toothed, green on the upper surface 

 and sometimes underneath; laeads few or numerous, 3 to 4 cm. high, the bracts ending 

 in sharp spines ; flowers dirty white . 



Above timber line the plants often flower when only 15 cm. high. 



4. Cirsium arvense (L.) Scop. Canada thistle. Occasional about Belton, along 

 the railroad and in cultivated fields. Native of Eur.; naturalized as a weed in N. 

 Amer. — Plants 0.3 to 1 meter high, with long rootstocks, green, glabrous or nearly so; 

 leaves with short lobes; heads usually numerous, about 2 cm. high, the bracts with 

 very short spines; flowers purple. 



The following family should have been inserted on page 326, preceding the San- 

 talaceae: 



LORANTHACEAE. Mistletoe Family. 



1. RAZOUMOFSKYA Hoffm. 



1. Razoumofskya americana (Nutt.) Kuntze. Occasional on the east slope, para- 

 sitic upon the branches of lodgepole pine. B. C. to Colo, and Sask. — Plants yellowish, 

 2 to 10 cm. high, branched, glabrous; leaves opposite, reduced to scales; flowers 

 .solitary, axillary, minute; fruit a small blue berry. 



