A, BRACTEOSA. 307 



2. A. 8ERENANA Nelson, in Abrams, Fl. Los Angeles, 128, April 5, 1904; Proc. Biol. Soc. Wash. 17 :99, April 9, 

 1904. — This name has been adopted by some American botanists for A. bracteosa Watson because of the 

 earlier A. bracteosa Trautvetter, Act. Hort. Petrop. l':17, 1870. This latter is synonymous with the still 

 older A. dimorphostegia Karelin and Kirilow, an Asiatic species. The name bracteosa is therefore available 

 for the American plant, according to the International Code. 



3. Obione bracteosa Durand and Hilgard, Pacif. R. R. Rep. 5': 13, 1858. — A. bracteosa Watson. 



4. — A slender, strictly erect, early maturing form of Atriplex bracteosa is sometimes found in the San Joaquin 

 Valley, California. It always grows, as far as known, in sod of Dislichlis spicata and Cynodon dactylon. The 

 foliage is yellow and sere by the middle of October, when the typical form in nearby fields is still green. No 

 differences can be found in the fruiting bracts or other essential characters, and the assumption is that it is 

 an ecologic or seasonal form. It is of some interest in connection with the curly-top disease of the sugar-beet, 

 since the leaf-hopper that transmits this disease is not carried over so late on these slender plants as on the 

 usual form. The following collections belong here: 5 km. northwest of Hanford, Hall 10970 (UC); near 

 Fresno, October 25, 1919, Hall (UC); between Bakersfield and Rosedale, Hall 11780 (UC); Rosedale, Davy 

 S922 (UC). 



5. — A supposed hybrid between A. bracteosa and A. argentea expansa has been collected near Ventura, 

 California (Hall 10964, UC). It is a rounded, bushy plant 7 dm. high with staminate inflorescences of the 

 former, but bracts as in the latter. The stems and branches are rigid, as in expansa. The leaves are similar 

 to those of bracteosa in shape and dentation, but larger, especially broader, and therefore somewhat intermediate. 



RELATIONSHIPS. 



Atriplex bracteosa is the end of an evolutionary line which began somewhere near A. pen- 

 tandra and threw off as short divergent branches A. p. muricata, A. barclayana, A. lini- 

 folia, and A. wrighti. This process was accompanied by a migration of the group from 

 the ancestral habitat in central or southern Mexico to the north and northwest. A. 

 bracteosa is restricted in its distribution to California, with only slight invasions across the 

 borders into Nevada and Lower California. It is thus well separated geographically from 

 its nearest allies. A. microcarpa, which belongs to the same general group, occurs also 

 along the coast of southern California, but this arose from another branch and reached its 

 present location by way of Lower California, whereas bracteosa has its closest affinities with 

 species of Arizona and New Mexico. Although these two species apparently hybridize, 

 as is indicated under minor variation 1, no intermediates occur and their connection can 

 be traced only through more primitive Mexican forms. 



The nearest approach to the common phylogenetic stock is through A. wrighti, which, 

 however, exhibits certain specialized features of its own. A. bracetosa differs from this 

 in the still more reduced size of the bracts and seeds, in the much less or scarcely com- 

 pressed fruits, and in having the leaves broadest below the middle and with smaller, 

 acute dentations. The foliage is not white beneath and the fruiting bracts do not have 

 the 3 nerves and fine reticulations which have been cited as evidence of the connection 

 between wrighti and muricata. 



ECOLOGY. 



Atriplex bracteosa was originally a moderate halophyte of the Distichlis zone especially, 

 but in recent years it has become the most characteristic weed of disturbed areas in the 

 San Joaquin Valley. It often covers fallow fields, roadsides, fenceways, etc. with a 

 dense pure community. The plants are exceedingly vigorous and produce abundant 

 seeds, so that they maintain the initial consocies for a longer period than usual. 

 Kearney and his associates have found a range of no alkali to 0.32 per cent in the first 

 foot of soil and 0.2 per cent in the second foot. The flowers appear from April to October. 



USES. 



This species is of no value, as it is not eaten by stock, but it is of some importance as 

 a cause of hay-fever. Its greatest interest, however, is in connection with the curly-leaf 

 disease of the sugar-beet. This malady has become so serious in some of the western 



