104 
IOWA ACADEMY OF SCIENCES. 
give the distribution and history of these weeds from informa- 
tion obtained from various floras, catalogues of plants, corres- 
pondence, and especially the larger herbaria of this country as 
Gray herbarium. Harvard University; Columbia College, her- 
barium; Missouri Botanical Gardens, Parry herbarium, U. Sv 
Department of Agriculture, and those of the Agricultural Col- 
lege. I wish to express my thanks to correspondents who have 
responded to requests for information. 
MARSH ELDER. 
Iva Xanthiifolia, Nutt. 
Description. An annual weed one to seven feet tall,, 
leaves all opposite, hoary withminute down, ovate rhombic or 
the lowest heart-shaped, doubly serrate or cut- toothed or 
obscurely lobed; heads small, crowded in axillary and terminal- 
panicles. 
In Gray’s Manual, 6th edition, the distribution of this weedi 
is given as follows: Northwest Wisconsin to Minnesota and 
Kansas westward. It must indeed originally have been quite 
local in many places in this region. It is only recently 
that this weed has attracted attention. I have known of the 
weed in southwestern Minnesota, near La Crescent, since 1884, 
where it occurred as an introduced plant along the embank- 
ments of a road. Strange to say, this weed did not occur on the 
east side of the Mississippi river as late as 1890. In 1889 and 
1890 this weed was growing in considerable quantity in a few 
places in the city of Boone, Iowa. The weed has made but 
little progress east of Boone. Ames is but fourteen miles dis- 
tant, but as yet the weed has not been found in this city. West 
of Boone, especially at Woodbine, in Harrison county, and in 
Crawford county, it is a very common weed. In Monona county 
it occupies many of the vacant lots. The writer has also 
observed it in Cerro Gordo county, but evidently it is just get- 
ting a foot-hold. J. C. Arthur writes me that he observed it in 
Charles City, Floyd county, in 1871. This county joins Cerro 
Gordo on the east. The writer has also received it from Fre- 
mont county, in southwestern Iowa. It is common in the Red 
River Valley of the North and other parts of Minnesota and 
Dakota, and in parts of Iowa along the Missouri river, as well 
as in Colorado. It is a very aggressive weed, as accounts by 
Upham, Bolley, Crandall and Bush indicate. At Missouri Val- 
ley, as far north as Onawa in the Missouri river bottoms, I 
