A. ARGENTEA. 



287 



are specimens of typical argentea from Antioch and San Joaquin County, central Cali- 

 fornia (July 4, 1902, Congdon, Gr, US; Cusick 688, Gr), and from San Bernardino, 

 California (August 20, 1893, McClatchie, NY); also specimens of expansa from north- 

 eastern Utah (C. P. Smith 2073, DS, SF). 



In some keys and descriptions these two subspecies are also differentiated by their 

 lower leaves, these being described as opposite in typica, alternate in expansa; but field 

 studies in California have demonstrated that the lower leaves of expansa also are opposite. 

 This finding has been verified by garden experiments in which the seedlings from 

 several different collections of seeds had uniformly opposite lower leaves. The error 

 as to the arrangement of the lower leaves doubtless has crept into the literature because 

 of the incomplete nature of most herbarium specimens. Many other characters used in 

 herbarium segregation of supposedly new species from A. expansa are now found to be 

 so variable, even on individual plants, that they can no longer be used. Some such are 

 almost certainly the result of a pathologic condition. 



Especially unreliable features are those that have to do with the "pedicels" and 

 sculpturing of the fruiting bracts. The former are of course only modified leaf-petioles 

 and their length is therefore subject to much variation. Long-stalked and sessile bracts 

 on the same plant is a common occurrence. The former condition is almost constantly 

 associated with the development of appendages on the faces. In some cases this is almost 

 a physical necessity, since the bracts are so compactly placed in the glomerules that any 

 considerable outgrowth of appendages necessitates an elongation of the base in order to 

 provide the space necessary for their development. If the appendage character is to be 

 used specifically, it should be so employed throughout the group at least. The futility 

 of such a course is demonstrated by a scrutiny of herbarium specimens, fully 50 per cent 

 of which exhibit both smooth and appendaged bracts on single stems (plate 44, figs. 

 10 to 15). 



Similar difficulties are encountered in an attempt to use the dentation of the leaves. 

 Throughout the whole species, but especially in expansa, there is a general tendency of 

 the leaves to be repand or sinuate-dentate. This shows even in dried specimens, through 

 the unequal folding of the margins. Finally, the distribution of the staminate flowers is 

 found to be far from constant. They are usually wanting in mature pistillate clusters, 

 but this is often because they have matured ahead of the fruits and been crowded off. 

 They sometimes form pure terminal spikes, although this can not be correlated with 

 other characters. The most notable examples of elongated staminate spikes or panicles 

 are found in a collection of expansa (Westminster, Orange County, California, June 20, 

 1896, McClatchie (UC) and in A. rydbergi (minor variation 9). The distribution of the 

 staminate clusters is perhaps correlated with nutrition factors, and, if so, it can have no 

 phylogenetic value. Since the characters just mentioned are thus found to be entirely 

 unreliable, the only course open is to refer all species based upon them to the category of 



minor variations. 



ECOLOGY. 



Atriplex argentea is one of the most widely distributed annuals of its genus, occurring 

 as a pioneer family or consocies in moderately alkaline areas throughout the West. While 

 the two subspecies are complementary in distribution, they exhibit essentially the same 

 ecologic behavior. Determinations of the salt-content by Kearney and his associates 

 have given 0.27 per cent in the first foot, and 0.2 for the second. It grows frequently 

 with Salsola, Suaeda, or Distichlis, as well as with other species of Atriplex. Both forms 

 often leave their alkaline habitat to become weeds in fallow fields and disturbed places, 

 usually constituting the initial stage of a short subsere. The plants bloom chiefly in 

 June and July, but they begin in May and sometimes last as late as October in moist 

 fields. The subspecies expansa is an important host-plant of Eutettix tenella (p. 308). 



