ON THE GENUS EUPHORBIA IN DECANDOLLE’S PRODROMUS. 443 
Trichosterigma, the 10th section, comprises 5 species, all of them Western Mexican, two of which 
reach into our boundaries. The two species of the 11th section belong to South America. 
The second great division, Exappendiculata, is divided into 16 sections, 2 of which only are 
represented in the North American flora. 
Sections 12 to 14 contain few species, none of them belonging to our flora. 
Section 15, Poinsettia, with 11 species, is almost entirely North American, or properly [290] 
Mexican ; 1 or 2 species extending farther south, and 6 reaching into our flora. The best 
known reumenniaties of this section, H. heterophylla, has been restored, recognizing E. cyathophora and 
L. graminifolia as varieties of the Linnean species. The New Mexican E. cuphosperma, which I had 
described as a form of edentata, is here described as a distinct species. EZ. eriantha ought to have 
been mentioned as also occurring in Arizona. It may be remarked that the name of Arizona does 
not occur in this or other botanical publications, as a district formerly of the Mexican State of 
Sonora; just as Louisiana even yet, after 50 years of separate existence, sometimes is used in botan- 
ical works for the Upper Missouri country. 
Sections 16 to 25, with 115 species, almost all belong to the Old World; they include the 
Euphorbie with succulent stems, those with the forms of Cacti. 
Section 26, Zithymalus, comprises the great mass of the Zuphorbie of the Old World. Of the 
302 species constituting it we furnish only 23, most of which belong to the southwest; 5 others 
have been sparingly introduced from Europe into the Eastern States. The sub-section Jpecacuanhe 
is the only sub-section of Zithymalus, whose ‘species, 19 in number, all belong to the New World: 
4 of them are peculiar to the Southeast; one comes over from the West Indies to the southern 
extremity of Florida, and allied as it appears to the Chilian forms, is peculiar to southeastern New 
Mexico. Of the sub-section Galarrhei (with obtuse glands), out of 108 species we have only 5 
native species, distributed from the Alleghany Mountains to Western Texas and California. The 
largest sub-section, Hsule (with two-horned glands), comprising 139 species, counts in our flora 12 
species, 2 of them in the Middle and Southern States, and all the rest belonging to Texas, New 
Mexico, and California. 
The 27th section is constituted by a single species, an Australian shrub. 
We find the name of two of our published species, viz., Z. commutata, Engelm. in Gray’s Manual, 
and £. Floridana, Chapm., in his Southern Flora, replaced by £. Ohiotica, Steud. & Hochst. and 
E. spherosperma, Shuttlew., names which have been published only on labels in distributed col- 
lections, while #. Riigeliana, Shuttlew., has not been substituted for #. Curtisii though published in 
the same manner. 
The following table exhibits the geographical distribution of the 80 species of Huphorbia, 
credited by M. Boissier to the flora of the United States. The immense extent of this flora may 
be properly divided into five districts. 
Flora of the Northern and Middle States, or the flora of Gray’s Manual, which however 
should naturally include the wooded part of Missouri, and exclude Northern Illinois and Wisconsin 
or the northwestern Prairie region. I adopt, however, Prof. Gray’s limits, adding Missouri. IT. 
Flora of the Southeastern and Southern States, east of the Mississippi, or the limits of Chapman’s 
Flora. III. Flora of the western Prairie Region from the British Possessions to the Rio Grande. 
IV. Flora of the Rocky Mountains, including the greater part of Washington and Oregon, the 
whole of Utah, Colorado, New Mexico, and Arizona. V. Flora of the Pacific slope of the continent. 
Some species extend through most of these regions, while others are common to several of them, 
and others again are limited to a single one; some extend into the extreme limits of our flora from 
the southern countries adjacent. The species, therefore, may be divided according to their geograph- 
ical extension into the following 12 classes :— 
Species common to the greater part of our territory. I class here Huphorbia Preslii, serpens, 
