14 BULLETIN 545, U. S. DEPARTMENT OF AGRICULTURE. 



Botanically Calamagrostis is closely related to Agrostis, the genus 

 to which redtop belongs, but may be distinguished from it by the long, 

 soft, fine hairs on the callus or hardened base of the floret and by the 

 prolongation of the axis of the spikelet behind the palea. 



Pine grass makes its most luxuriant growth in the Transition zone, 

 where it grows mainly under the relatively open forest of western 

 yellow pine (Pinus ponderosa) . It is also found in the Canadian zone, 

 where it often ranks first in abundance and importance among the 

 grass species. In the Hudsonian zone it is found only in the warmer 

 situations of the lower altitudes. (See Plate IX.) 



Pine grass (Plate X) may be recognized by its perennial character 

 and its^ abundant, well-developed, creeping rootstocks which produce 

 a continuous, closely matted sod or turf. The culms, somewhat 

 bunched, grow from 1 to 3 feet tall, and usually bear three short, 

 smooth leaves ; the rather numerous lower or basal leaves are somewhat 

 involute, flexible, and smooth. The panicle, pale green until the 

 plant is mature, is contracted and densely flowered, the spikelet 

 bearing but one floret. One pronounced character by which the 

 species may be recognized at a glance is the ring of stiff hairs at the 

 junction of the sheath and blade. 



The fibrous, widely spreading and deep root system, make it 

 possible for pine grass to grow in exposed situations where the soil 

 is relatively dry during most of the growing season. (Tests for 

 drought resistance show that this species usually fails to regain its 

 form after wilting notably in a soil containing an average water 

 content of 8.5 per cent. In the case of two specimens turgor was 

 regained in a soil which contained but 5.5 per cent of moisture.) 



Owing to the warm and relatively dry situations generally inhabi- 

 tated by pine grass, the flower stalks begin to appear about July 1. 

 The number is comparatively small, and production continues until 

 September 1 . On the higher areas flower-stalk production is invaria- 

 bly sparse, with the period of production extending from July 20 to 

 the end of the season. The seed begins to ripen on the lower ranges in 

 late July, and the period of maturity extends until the middle of 

 September. On the higher ranges the first seed ripens by August 

 10, and the maturing period lasts until unfavorable weather condi- 

 tions in September. Seed of the last flower stalks produced seldom 

 ripen. 



In fertility, the seed of pine grass l ranks about the highest of the 

 native species studied. The lowest vitali ty observed occurred in 1 907, 

 when an average of 58.2 per cent was obtained. In 1908 and 1909 

 averages of 76 and 74.5 per cent, respectively, were secured. Seed 

 collected at different times in the Transition zone yielded the highest 



* The seed used in these tests was collected in the upper Canadian zone in the latter part of August of 



