weed as the taproot is fleshy, penetrating the soil to a depth of 

 a few inches only, and an ordinary plowing would kill most of 

 the plants disturbed. It is lamentable that more of our intro- 

 duced plants do not add to the beauty of the country instead 

 of increasing the farmer's woes. 



In Pedro Valley, a few miles south of Colma, Mercurialis 

 annua L. is well established in an artichoke field thirty or forty 

 acres in extent. The entire field is pretty well infested and the 

 pistillate plants set an abundance of seed. It is difficult to fore- 

 tell how troublesome this weed may become, but the history of 

 other European weeds transplanted to America and the pro- 

 lific seeding propensities of Mercurialis bode ill for the truck 

 farmers of the district. 



This weed was reported in the United States for the first 

 time, so far as I am aware, in 1856, when Dr. Gray 1 listed it from 

 Boston, and Charleston, South Carolina. It may have been pres- 

 ent in other parts of the south also for in 1901 Mohr wrote of 

 its presence in Alabama, "Mobile, ballast weed, observed for 

 over 30 years, common about the shipping." 2 A few years later 

 Britton and Brown gave its range as, "In waste places, Nova 

 Scotia to Florida, Ohio and Texas." 3 It seems to have been 

 making steady progress westward and has finally reached the 

 Pacific Coast. That it did not reach California much earlier can 

 probably be accounted for by recalling that the plant must de- 

 pend almost entirely upon human agencies to distribute the 

 seed. 



It is to be hoped that Mercurialis will prove less trouble- 

 some to the farming areas of California than has the introduc- 

 tion of such weeds as Lepidium draba, Tribulus terrestris, Hor- 

 deum murinum, and Centaurea solstitialis. 



Dudley Herbarium, 

 Stanford University, 

 California. 



1 Gray, Asa, Man Bot. 393. 1856. 



2 Mohr, Charles, Plant Life of Alabama 594. 1901. 



3 Britton, N. L. & Addison Brown, 111. Fl. N. U. S. & Can. ed. 2. 2: 460. 

 1913. 



