260 GENUS ATRIPLEX. 



and their allies of the Old World can not be satisfactorily worked out at this distance. 

 It may be suggested, however, that because of its evident connection with A. patula 

 glabriuscula, A. maritima is perhaps the most primitive, while A. tatarica evidences a 

 higher degree of specialization than the others in the much more thorough separation 

 of the two sexes in the inflorescence. 



Because of its absence from all but the more recent American manuals, Atriplex 

 rosea has been often wrongly identified. The inferior, or at least lateral position of the 

 radicle is often overlooked and plants are then especially confused with A. argentea, 

 A. bradeosa, and A. pentandra arenaria. It may be distinguished from the first by the 

 narrower leaves, which taper to the base and are more sharply dentate; from bracteosa 

 it differs in its much paler foliage and in the absence of the long, moniliform or spike- 

 like staminate inflorescences; while pentandra arenaria may be easily recognized by the 

 essentially entire and usually obtuse leaves. There are, of course, other and more 

 constant although less obvious characters upon which these species are separated. 



ECOLOGY. 



Atriplex rosea, although an introduced weed, is so abundant in the West, especially 

 in the arid portions, that it plays an ecological role of great importance. It is most char- 

 acteristic of roadsides, fallow fields, and waste places, where it is often the pioneer 

 consocies of the subsere, but it has also become abundant in alkaline valleys and plains, 

 where it may form pure consocies, or may be mixed with native species of Atriplex or 

 other halophytes. It is exceedingly variable in habit, ranging from typically branched 

 forms a meter or more high to giant tumbleweeds 2 to 3 meters tall and wide. Under 

 intense competition the plants are slender and unbranched and in extreme conditions 

 they become dwarfs but a few centimeters in height. The tumbleweed habit has 

 doubtless played a large part in the rapid migration of this species throughout the West, 

 as it also explains its abundance in f enceways and roadsides. Owing to its size and abun- 

 dance, this is one of the most important host-plants of Eutettix tenella, the leaf-hopper 

 that carries the curly-top disease of the sugar-beet. In the West the plants bloom 

 from July through September. 



USES. 



The herbage of the red orache has many uses in Europe, but none of them are of 

 prime importance. Potash is obtained from it in Greece and it is utilized to a limited 

 extent in medicine as an antiscorbutic and as a corrective for scrofula. No detailed 

 study of the forage value of the plant has been made in America. In some parts of 

 Nevada the young plants are highly prized for feeding to swine. It is said to be the 

 cheapest and most satisfactory feed there available for fattening. On the other hand, 

 recent experiments indicate that the plants are mildly poisonous to sheep when fed in 

 large amount and to the exclusion of other material. An analysis is given by Suarez 

 y Bermudez (Exper. Sta. Rec. 33:466, 1915). The plants grow so readily in the western 

 States and on such poor soil that their possible utilization for stock-feeding, both direct 

 and as silage, should be thoroughly tested. 



The pollen has been found to be one of the causes of hay-fever of the late summer 

 type in the West. Preliminary studies indicate that all species of the genus probably 

 are potential causes of this malady, their relative importance depending more upon 

 the abundance in which the plants grow in the populated districts than upon the spe- 

 cific properties of the different kinds. It does not follow, however, that an individual 

 sensitive to one species is necessarily sensitive to all, since it is found that patients react 

 differently to pollen of the various species. An extract of the pollen is used in making 

 the tests, which consist of intradermal injections of extremely dilute solutions. If such 



