HITCHCOCK AND CHASE NORTH AMERICAN PANICUM. 231 



135. Panicum thermale Boland. 



Panicum thermale ^Boland. Proc. Calif. Acad. 2: 181. 1862. "On hot rocks and 

 in hot water flowing from the Geyser springs and Geyser mountains, in the northern 

 part of Sonoma County," California. The type, in the Gray Herbarium, is the early 

 branching form. It is marked "I call this: Panicum thermale till I shall know, 

 better. It grows in the Geysers Sonoma Co. and on hot rocks." 



Fig. 243.— P. thermale. From 

 type specimen. 



DESCRIPTION. 



Vernal culms grayish green, densely tufted, velvety-villous, 10 to 30 cm. high, 

 ascending or spreading, the nodes with a dense ring of short hairs; sheaths often over- 

 lapping, velvety-villous; ligules 3 mm. long; blades thick, ascending or spreading, 

 3 to 8 cm. (mostly about 5 cm.) long, 5 to 12 mm. wide, acuminate, rounded or sub- 

 cordate at base, both surfaces densely velvety-villous; panicles exserted or in high 

 alpine specimens partly included, 3 to 6 cm. long, about as wide, densely flowered, 

 the axis villous, the flexuous branches spreading, often drooping; spikelets 1.9 to 2 



mm. long, 1 mm. wide, obovate-oblong, obtuse, 

 turgid, papillose-pilose; first glume about one- 

 third the length of the spikelet, obtuse or abruptly 

 pointed; second glume and sterile lemma sub- 

 equal, the glume shorter than the fruit at ma- 

 turity; fruit 1.7 mm. long, 1 mm. wide, elliptic, 

 subobtuse. 



Autumnal form widely spreading, the branches 

 appearing even before the primary panicles are 

 exserted, repeatedly branching, the whole form- 

 ing a dense cushion, the blades and panicles of the ultimate branchlets reduced; 

 winter rosette appearing early, the blades ovate-lanceolate, usually less pubescent 

 than those of the culms. 



In the original description Dr. Bolander states: "The whole plant is like velvet to 

 the feel. There are, however, some specimens which are rather smooth." This 

 smoother form is represented by part of Merrill 157, one tuft of which has lower blades 

 nearly glabrous, but sheaths and upper blades nearly as velvety as in the type, while 

 other specimens of this collection are fully as villous. The Bolander type collection 

 represents about the average of the species. Some of the specimens cited below are 

 longer villous than the type and some few are smoother. 



A specimen from Banff, Alberta, McCalla 2318, "on tufa and old bogs in warm 

 sulphur stream; alt. 4,500 ft.," has 

 short, early-branching culms, broad 

 leaves and small panicles like P. ther- 

 male, but the pubescence is of sparser 

 long hairs, somewhat harsh and promi- 

 nently papillose as in P. pacijlcum. 



DISTRIBUTION. 



Wet saline soil in the immediate 

 vicinity of geysers and hot springs 

 ascending to 2,500 meters, Alberta to 

 Wyoming and California. 



Alberta: Banff, McCalla 2318. 



Montana: Lo Lo Hot Springs, Williams & Griffiths 306. 



Wyoming: Yellowstone National Park, Chase 5252; Hitchcock 1902, 2061, 



Mearns 3061, 4050, 4166, 4203, 4789, 4870, 4983, 5061, 5110, 5134, Merrill 15/ 



Fig. 244.— Distribution of P. thermale. 



