CATALOGUE. 253 



plants, 2-4' high, \-l" thick at base ; fertile plants much smaller ; flowers 

 small, staminate ones 1" wide, lobes ovate-orbicular, acutish ; pistillate 

 flowers £-1", fruit 2" long. — Only on Pinus contorta, Rocky Mountains to 

 Oregon and California ; near Breckenridge, at 10,000 feet altitude, Wolf, 

 1873. Flowers late in autumn. — In this and the next, species, accessory 

 flowers or flowering branchlets are developed on the fruiting specimens, in 

 this lateral, in the next dorsal to the fruits or fruiting branches. In these 

 two we find no other secondary formation on the fertile plants, but in the 

 other species stei-ile branchlets are developed on them which would flower 

 in the following year ; thus these latter continue their existence for a longer 

 time than the two first ones. 



Arceuthobium Douglasii, Engelm. ined. — Slender, small, \-\' high, 

 greenish-yellow, dichotomously branched; branches suberect, single or 

 with accessory ones behind the first ; flowers in short, usually 5-flowered, 

 spikes, staminate ones less than 1" wide, with orbicular-ovate acutish lobes ; 

 fruit 2£" long. — On Pseudotsuga Douglasii from New Mexico (on Santa Fe 

 River, Rothrock, No. 69, 1874J to Utah, Parry, Siler, and Northern Ari- 

 zona, Camp Apache, G. K. Gilbert (109), 1873.— Flowers May-June.— 

 Similar to the last, but smaller, and never with verticillate branchlets or 

 flowers, which are so common in that species The thallus-like tissue or 

 stroma, which creeps along within the bark of the nurse plant, buds out in 

 autumn all along the three years old shoot; after about 12 months, the 

 flower-buds are formed, to open in the following spring, after which the life of 

 the male plant is exhausted ; but it takes another year to perfect the fruit. 

 The female parasite, now fully three years old, generally dies, but sometimes 

 lives and fructifies another season. The Northeastern A. pusillum, Peck, 

 behaves in the same manner, while in A. Americanum and some other 

 species the buds of the parasite make their appearance at first only among 

 the older bud-scales of the pine branch. 



Var. ? microcarpum is parasitic on Picea Engehnanni, found by Mr. 

 Gilbert in 1873 (100 and 102) in the Sierra Blanca, Arizona; it is a little 

 taller, 1-2' high, but has much smaller fruit, only If" long, the smallest, 

 of any American species. 



Arceuthobium divaricatum, Engelm. ined. A. campylopodum, var. 



