6 BULLETIN 800, TJ. S. DEPARTMENT OF AGRICULTURE. 
A. subverticiUata. In our opinion there is only one species of this type in New 
Mexico. 
The study of fresh specimens in Xew Mexico, Colorado, Utah, and 
the examination of dried specimens in the herbaria leads to the con- q 
elusion that A. verticillata does not occur in the Rocky Mountain 
country, but is a species of the Atlantic Plains and the Mississippi 
Valley. 
A. mexicana grows from 3 to 5 feet high, and has wider leaves and 
shorter horns than other species of the whorled-milkweed group. It 
ranges from southern Mexico through western Arizona, California, 
and western Nevada to the Columbia and Snake River valleys in 
"Washington and eastern Idaho. 
A. pumila (A. verticillata var. pumila) is a low. tufted plant with 
leaves irregularly crowded on the stem. The plant, if it proves to be 
only a variety, belongs with A. galioides. It ranges from South Da- 
kota to Colorado, western Xebraska, and Xew Mexico. 
A. galioides was included by Dr. Gray in A. verticillata. Recent 
authors have tried to distinguish the two species by the shape of their 
hoods, describing those of A, verticillata as entire from a rear view, 
and those of A. galioides as hastate-sagittate. 
All the whorled-milkweed flowers seen in the summer of 1918 had 
entire hoods. Examination of these specimens after drying shows the 
hoods hastate-sagittate. A study of herbarium specimens indicates 
that hoods of both A. verticillata and A. galioides are often hastate- 
sagittate when dried. These species, however, differ in two respects. 
A. verticillata has a Bunch of long, fibrous roots and smooth pods; 
A. galioides has horizontal main roots and hairy pods, and in these 
characters agrees with A. pumila and A. neexicojna. In flower the 
species appear to be nearly identical. 
There appears to be no doubt that the plant which has been respon- 
sible for the cases of poisoning in Colorado, Utah, Arizona, and Xew 
Mexico is A. galioides. 
DISTRIBUTION AND HABITS OF THE PLANT. 
The plant ranges northward from Central America through Ari- 
zona and Xew Mexico to central Utah and central Colorado. 
It has been found in Utah as far north as Beaver County (?ccord- 
ing to Esplin) and the foothills of the Uinta Mountains (according 
to Jones). In western Colorado it has been seen on Grand River as 
far up as Glenwood Springs, on the Xorth Fork of the Gunnison 
River as far as Bowie, and on the Gunnison River to the Black 
Canyon. 
In eastern Colorado it has not been observed north of the Arkansas 
watershed, but occurs on that river as far as Parkdale, just above 
the Royal Gorge. Figure 1 shows, in a general way, its distribution. 
