GEAZING EANGES IN SOUTHERN ARIZONA. 17 



necting C and I on the map (fig. 2). It was difficult to find any 

 black grama in the field.^ In 1914 the perennial grasses had pushed 

 northwestward along the Tucson road at least 1^ miles, if not 2 

 miles, farther than they extended about five years before, and w^ere 

 established about 1 mile farther west along the south side of the 

 field. The crowfoot grama has reached the north fence, not as a 

 pure stand, but as the most important element of a well-developed 

 though not yet complete grass association. In this same area the 

 black grama is now abundant and spreading. Along the west fence 

 is an area where the black and wire gramas are becoming abundant 

 and important. In the southwest corner is an area of a section or 

 more where ray less goldenrod {Isocoma hartwegii) showed a scat- 

 tering growth in 1903.^ This same area is now thickly covered with 

 large mature plants of this species (PL V, figs. 1 and 2), a large 

 number of w^hich are dying, probably as the result of the encroach- 

 ment of the grasses which are gradually taking possession of the 

 area.'^ The rayless goldenrod is of no value as a forage plant and 

 it is customary to think and speak of it as a range weed and a 

 nuisance. But it certainly protects the soil from erosion, retards 

 run-off, and furnishes conditions favorable to the germination of 

 the grass seeds. The grasses will probably eventually crowd it out. 



One of the most noticeable features of the grass-covered area of 

 the reserve is the prevalence of spots a few square yards in extent 

 covered by an almost pure stand of some long-lived perennial grass. 

 This habit is more or less characteristic of the black grama {Muhlen- 

 hergia forteri)^ but especially true of the wire grama {Bouteloua 

 eriopoda) , and of a coarse grass called Heteropogon contortus (PL 

 III, fig. 2). The two first named are valuable forage plants; the last 

 is usually considered undesirable. 



Measurements show what is very plain to simple observation, that 

 the Heteropogon puts a relatively large crop of feed on the ground. 

 But this feed is almost valueless while green because the animals do 

 not like it, and the grass is usually avoided in the hay cutting because 

 of the large, sharp seeds that hurt the mouths of the animals. In 

 1911 about 100 pounds of this grass was cut and cured just before it 

 commenced to seed. It made a very good quality of hay, which was 

 eaten by one of the work horses w^ith relish and in preference to old 

 grama hay of the previous season. It would seem that this grass 

 may have a possibility as a hay crop, if cut at the proper time. It is 

 a long-lived, strong-rooted perennial that spreads by rootstocks and 

 grows about 2 feet high. 



1 See Bureau of Plant Industry Bulletin 177, PI. IV, fig. 1, photographed in November, 

 1902. 



2 See Bureau of Plant Industry Bulletin 177, PI. IV, fig. 2, photographed in June, 1903. 



3 The comparative data here given are supported by the testimony of Mr. W. B. 

 McCleary, who has known this range for the past 15 years and who drove over a large 

 part of it with the writer in September, 1914, for the purpose of making comparisons. 



28465°— Bull. 367—16 3 



