LORANTHACEAE 145 



nearly equaling the leaves: pistillate panicles denser and shorter. Abundant 

 in the Wasatch and westward throughout California. 



3. Urtica gracilis Ait. Hort. Kew 3: 341. 1789. Usually tall and rather 

 strict, slender, sparingly bristly: leaves ovate-lanceolate, serrate, 3-5-nerved 

 from the rounded or scarcely heart-shaped base, glabrate or slightly pubescent, 

 the veins and the elongated" slender petioles more or less hispid : spikes slender 

 and loosely panicled. (U. cardiophylla Rydb. Bull. Torr. Bot. Club 24: 191. 

 1897 and U. gracilipes Greene are forms only; the former with subcordate leaves; 

 the latter with leaves glabrous, more elongated, and more slenderly petioled.) 

 Montana to New Mexico and far eastward. 



34. LORANTHACEAE D. Don 



Evergreens, parasitic on shrubs or trees, dull yellowish-green or brownish, 

 with dichotomous branches and swollen joints, the opposite thick and coria- 

 ceous exstipulate and entire leaves reduced to mostly connate scales. Flowers 

 small and inconspicuous, greenish, dioecious, of 2-5 sepals coherent at base. 

 Anthers as many as the sepals and inserted upon them. Ovary inferior, 

 1-celled. Fruit a berry with glutinous endocarp. 



Anthers a single globose cell; berry compressed, fleshy . . .1. Arceuthobium. 

 Anthers 2-celled; berry globose, pulpy . . . . . .2. Phoradendron. 



1. ARCEUTHOBIUM Hoffm. LESSER MISTLETOE 



Parasitic on conifers, glabrous with rectangular branches and connate scale- 

 like leaves. Flowers often crowded into apparent spikes or panicles, opening in 

 summer or autumn and maturing their fruit in the second autumn, when the 

 berries suddenly and forcibly eject the glutinous seed to the distance of several 

 Flowers axillary or terminal, solitary or several from the same axil. 



Staminate flowers on peduncle-like joints in a paniculate cluster. . 1. A. americanum. 

 Staminate flowers in the axils of the scales of a simple or compound spike. 



Spikes short, stout, 3-4 mm. in diameter . . . . .2. A. cryptopodum. 



Spikes slender, 1-2 mm. in diameter. 



Dark, usually greenish-brown . . . . . . . 3. A. divaricatum. 



Pale, usually yellowish-green. 



Flowers few (host Douglas Spruce) 4. A. Douglasii. 



Flowers many (host Limber Pine) . . . . . 5. A. cyanocarpum. 



1. Arceuthobium americanum Nutt. ex. Gray, Bost. Journ. Nat. Hist. 

 6: 214. 1S')(). Slender, dichotomously and verticillately much branched, 

 greenish-yellow: staminate plants 5-10 cm. high: fertile plants much smaller: 

 flowers small; the staminate 2 mm. broad, lobes ovate-orbicular, acutish; the 

 pistillate 1-2 mm. broad: berry 4 mm. long. On Pinus flexilis, P. Murrayana, 

 and probably P. edulis. Idaho to Colorado. 



2. Arceuthobium cryptopodum Engelm. in Gray, PI. Lindh. 2: 214. 1850. 

 Stout, 5-10 cm. high, 3-5 mm. thick at base, paniculate, much branched, 

 brownish-yellow to dark olive-brown: staminate plants smaller than the 

 pistillate ones; staminate spikes with much compressed buds: flowers mostly 

 3-parted, 3-4 mm. broad: anthers attached above the middle of the ovate 

 acute lobes: fruit 4-5 mm. long. On Pinus scopulorum. Colorado and south- 

 ward. 



3. Arceuthobium divaricatum Engelm. Bot. Wheeler Survey, 253. 1878. 

 Rather slender, the branches spreading, often recurved, 5-10 cm. long, olive- 

 green or light brown: staminate flowers few and scattered, or in 3-7-flowered 

 spikes, 2 mm. in diameter, with ovate acute lobes: inflorescence often bearing 

 sterile branches from the same axils as the fertile ones: fruit 3-5 mm. long. 

 On Pinus edulis. Colorado and to the southwestward. 



4. Arceuthobium Douglasii Engelm. 1. c. Greenish-yellow: stems slender, 

 6-24 mm. high, much branched but not verticillately: spikes short, mostly 



ROCKY MT. BOT. 10 



