278 



S. B. PARISH 



Another river-bottom plant which has become common is the 

 annual grass Leptochloa imbricata. The inhabitants, recognizing 

 the means by which it is distributed, give it the name of "water 

 grass. " It ripens an abundance of seed, which is readily shattered 

 out, and in the climate of the Valley probably is reproduced by 

 germination more than once in the year. As a crop weed it appears 

 mostly in alfalfa fields. I have seen some in which the grass made 

 quite as much a show as the legume. While it doubtless has some 

 feeding value it cannot but deteriorate the xahiQ of hay in which it 

 is present in any considerable amount. 



Echinochloa colona is also frequent in alfalfa fields, and along 

 the streets and in the yards and lawns of the towns. Other weeds 

 common in such places are Leptochloa imbricata, Amaranthus 

 Palmeri and Physalis Wrightii, all of which have been mentioned 

 as frequent elsewhere. Atriplex semibaccata is almost exclusiveh' 

 a ruderal weed, and as such is abundant in places, as near Imperial. 

 Sida hederacea, known as Running Malva, is troublesome in places, 

 and is very difficult to eradicate. It probably comes in from the 

 bottom lands of the Alamo and New Rivers, two tributaries of 

 the Colorado delta which penetrate the Valley. From the same 

 sources Lippia nodiflora and Sesuvium sessile sometimes make 

 their way into the fields on the adjacent bluffs, but they have not 

 become pests. 



In addition to the indigenous plants which have assumed the 

 role of weeds, there are some introduced plants of the Colorado 

 bottoms which have entered the Valley through the irrigation sys- 

 tem. The commonest of these is Eclipta alba, a cosmopolitan 

 plant of tropical and subtropical regions. This is very abundant, 

 making a luxuriant growth on the banks of canals, and is one of the 

 commonest weeds in waste places. The cockle-bur of the Vallej', 

 Xanthium commune, also comes from the Colorado river-bottom, 

 where it is common. It is widely diffused throughout the Valley, 

 and in places abundant. This species is unknown in the older 

 settlements of southern California, where its place is taken by 

 Xanthium canadense. The derivation of Aster ezilis and Eriger- 

 on canadense is uncertain, as they are alike common along the lower 

 Colorado Ri-\'er and in the other valleys of California, but their abun- 



