304 GENUS ATRIPLEX. 



2. Obione microcarpa Bentham, Bot. Voy. Sulph. 48, 1844.—^. microcarpa Dietrich. 



3. — A very distinct form or subspecies, apparently connecting with A. pentandra muricata, of Mexico, comes 

 from Lower California and the islands to the west. This is a small annual with prostrate lower branches, 

 narrowly spatulate leaves, and fruiting bracts sometimes as much as 4 mm. long through the development of 

 a prominent terminal lobe, or tooth. Most of the bracts, however, even on the same plant, are only about 

 2 mm. long and exactly like bracts of the common form of microcarpa. This variation apparently is well 

 isolated geographically from the more northern type. Collections at hand include: Natividad Island, April 

 10, 1897, Brandegee (UC); San Benito Island, Anthony 877 (DS, UC, US); San Jose de Gracia, April 8, 1889, 

 Brandegee (UC). 



RELATIONSHIPS. 



All available evidence indicates that this is a derivative of A. pentandra through its 

 Mexican subspecies muricata. The two are identical in essential features, such as posi- 

 tion of embryo, distribution of the two kinds of flowers, and general shape of bracts and 

 leaves. A. microcarpa exhibits the greater specialization, especially in the almost con- 

 stantly reduced staminate inflorescence, reduced size of bracts and leaves, more uniform 

 suppression of bract-margins and bract-appendages, and constantly annual habit. These 

 modifications apparently arose in connection with the northwesterly migration of the 

 group. Genuine muricata stops at the western shores of the Sonoran Coast; microcarpa 

 now begins about half-way up the peninsula of Lower California, on the Pacific side, and 

 ranges thence northward. The connection between the two seems to be established by 

 minor variation 3 of the latter species, which comes from that portion of the range of 

 microcarpa which is nearest to that of muricata. The reductions indicated above are 

 mostly quite evident in this, except that the staminate inflorescence sometimes is even 

 more elongated than in any known form of muricata and some of the bracts also are as 

 in muricata, while the leaves are intermediate and with their own pecuUar shape. How- 

 ever, the elongated inflorescence is a feature of only one of the twelve plants at hand and 

 may be either abnormal or a development representing a local strain. In other plants 

 of the same collection (Natividad Island, Brandegee) the staminate glomerules are all 

 axillary. The bracts on this intermediate form vary all the way from broadly winged, 

 and therefore as large as in muricata, to nearly wingless and as small as in microcarpa. 

 Most of them are of this latter type and the sides are not appendaged. 



The phylogenetic connection just discussed was first suggested by Bentham in con- 

 nection with his original description of the species. Bentham attempted to include also 

 A. barclayana in the group, the material then available giving no indication that this 

 species was chiefly dioecious, as has been since established. Other features also now 

 indicate that, while A. barclayana belongs somewhere near, it is better considered as a 

 divergent line which stands close to the beginning of a large group of species character- 

 ized by a shrubby and dioecious habit. There is now no reason to suppose that micro- 

 carpa evolved by the roundabout route of barclayana, and, moreover, there would be 

 several insurmountable objections to such a theory. 



ECOLOGY AND USES. 



Atriplex microcarpa forms small clan-like groups in sandy soil back of the strand, and 

 occurs also as a subruderal along roadsides. The flowers open for the most part from 

 March to June, but have been found as late as October. 



No uses are known for this species, though it is possibly an occasional cause of hay- 

 fever, 



28. ATRIPLEX WRIGHT! Watson, Proc. Am. Acad. 9: 113, 1874. Plate 47. 



Erect or ascending annual herb, 2 to 8 dm. high, the branches few and the plants bush- 

 like; branches thick, deeply grooved, sparsely scurfy, soon glabrate and then stramineous 

 or reddish; leaves alternate, numerous, mostly short-petioled, oblanceolate to elliptic- 

 spatulate, all much narrowed to the base, obtuse and mucronulate or the upper ones 



