346 GENUS ATRIPLEX. 



The second group of subspecies consists of linearis and macropoda, both inhabitants of 

 the arid Southwest. They are characterized by narrower leaves and mostly smaller 

 fruiting bracts than are found in typica, but it will be noted from the descriptions that 

 there is a considerable overlapping in these features. Forms intermediate between 

 linearis and typica are too numerous to justify the retention of the former in specific rank. 

 The collections of macropoda are too meager to permit of definite statements, but its prin- 

 cipal character, the elongated stalks to the fruiting bracts, is almost certain to vary to a 

 considerable extent and not in unison with other features. 



ECOLOGY. 



Atriplex canescens is by far the most widely distributed of all the shrubby species of 

 the genus. While its original role was evidently as a consociation of the Basin sagebrush 

 association, it occurs in the mixed prairie of the western Dakotas and Nebraska, the 

 desert plains and desert scrub of the Southwest, and in the Coastal sagebrush of Cali- 

 fornia. Though it has a wide range of adaptability, growing from Sarcobatus flats to 

 grassland valleys with practically no alkali, it is usually found in soils with a salt-content 

 ranging from 0.03 to 0.10 per cent. In the Basin sagebrush association, A. canescens 

 typically occupies well-drained valleys, while in the Coastal sagebrush it runs from the 

 edge of alkaline depressions well into the mixture of Artemisia, Salvia, Eriogonum, and 

 Pentstemon, or occurs in peculiar forms along the seashore back of the strand. It is 

 frequent in alkaline flats in desert plains and scrub from western Texas to the Mojave 

 Desert, often associated with A. polycarpa, and less often with lentiformis. It is a regu- 

 lar associate with Prosopis on the dunes formed by the latter, from the White Sands of 

 New Mexico to the dunes of the Imperial Valley, though in itself it is a poor dune-former. 

 This universal tendency to form a subclimax that is post-climax in nature is further seen 

 in the OUgocene bad-lands of the Black Hills region, where it is frequent in ravines and 

 on more stable slopes . 



USES. 



This species is exceptional in the genus for its economic value. Its vigorous growth 

 and masses of wing-fruits give it considerable worth as an ornamental in somewhat alka- 

 line soils, where it also may be grown into a serviceable hedge. Its chief importance, 

 however, is for grazing. It is the most palatable of the shrubby species, at least, and 

 possesses unique value during drought periods when the grass crop is short. It has been 

 successfully introduced into the desert plains at Tucson, Arizona, and can probably be 

 grown with even greater success in the other associations of the grassland formation. Its 

 value in the Southwest has been discussed by Griffiths (U. S. Dept. Agr. Bur. Plant 

 Ind. Bull. 4:17, 1901). As a form of insurance against recurrent drought periods it 

 deserves a permanent place in grazing economy. 



Reports that the herbage is poisonous to stock have led to a detailed chemical and 

 experimental investigation by the Nevada Experiment Station, the complete results of 

 which are not yet ready for publication. Analyses made by Miller, the chemist at this 

 station, reveal the presence of saponin in large amounts, of pectins, and of glucosides. It 

 is beUeved by Miller that the glucosides are not injurious, but that poisoning, if.it occurs, 

 is due to the saponins. Experiments on sheep indicate that the plants are sometimes 

 harmless, while in other cases death results. It is probable that the high value of Atri- 

 plex canescens when browsed under normal conditions and when mixed with other feed 

 much more than offsets its possibly injurious effects in certain cases. 



The seeds of this and other shrubby species are ground into meal by the Indians and 

 mixed with other flours in the preparation of food. The pollen has been found to be a 

 cause of hay-fever in a few cases and therefore is used in the preparation of immunization 

 extracts. 



