442 ON THE GENUS EUPHORBIA IN DECANDOLLE’S PRODROMUS. 
M. Boissier describes 693 species, which for the greatest part he had seen and carefully analyzed 
himself, and adds 30 others as incompletely known, thus constituting the most numerous genus 
known, after Panicum, of which Steudel enumerates 864 species, and larger than Senecio, of which 
DeCandolle knew 601 species. These species are arranged into two great divisions, the Appendiculata, 
with petaloid appendages to the glands of the involucrum, and the Lvappendiculate, without such 
appendages. The former, containing 253 species, are for the greater part found in America: the 
latter, with 440 species, principally inhabit the Old World. This division of the genus is probably 
the most natural that could be made, though the first five species of the division are calle 
M. Boissier himself Gymnadenie, thus referring them properly to the second division, and [289] 
though other closely allied forms, such as £. corollata and #. [pecacuanhe, had to be widely 
separated on account of the difference in this particular. 
The Appendiculate are divided into 11 sections, the first and largest of which is Anisophyllum 
with 176 species, the best known representatives of which with us are ZL. maculata and £. hyperici- 
folia, here called E. Preslii. We have in our flora 36 species of this section ; one of these, EZ. Presiit, 
is spread over the whole of North America; 6 are found in the Mississippi valley or east of it; 3 
common in the West Indies, extending into Florida (of these 2. hypericifolia, L., proper, is not men- 
tioned as a Florida plant by M. Boissier); 24 are peculiar to the western plains, Texas, New Mexico 
and Arizona, and 2 are exclusively Californian. Several of the 24 southwestern species extend farther 
south into Mexico, and 2 of them, Z. prostrata and £. serpens, which latter extends up the Missis- 
sippi and its confluents, are wide-spread species found through the warmer parts of the whole 
globe. 
M. Boissier has recognized several forms as distinct species in which I have only been able to 
see so many varieties of one polymorphous species. Thus the old £. hypericifolia comprises his 
small-flowered and fruited tropical £. hypericifolia proper, our larger-flowered, larger and darker- 
seeded £. Preslii, and several tropical and eastern forms, as the hairy-fruited #. lasiocarpa, the large- 
seeded #. Brasiliensis, and others. JL. zygophylloides was very properly separated from £. petaloidea, 
but £. polyclada I suspect is only a form of the latter. #. mieromera, which I had taken for a form 
of #. polycarpa, seems well distinguished. I may add here that the western £. serpyllifolia, formerly 
united by me to several forms of the Old World under the name of FZ. inequilatera and E. glypto- 
sperma, has lately been found by Mr. T. J. Hale in Wisconsin; as also #. Geyeri, first discovered in 
Illinois, which last seems to preserve its distinction from Z. petaloidea. 
The second section, Zygophyllidium, comprises 4 species, of which 3 belong to the southwest and 
one to Mexico. 
The 25 species of the 3d section, Cyttarospermum, are all inhabitants of the warmer parts of 
America, 13 being Mexican, and only one of our species, Z. bifwreata, perhaps an intermediate link 
between this and the former section, is doubtfully referred here. 
Sections 4 and 5 contain few (only American) species, none of them belonging to our flora. 
Section 6, Petaloma, consists of 3 species, two of which, Z. marginata and £. bicolor, belong to 
the west and southwest, and the third is a closely allied Mexican form. 
Sections 7 and 8 are small and almost entirely South American. 
The 9th section, Tithymalopsis, on the contrary, is entirely North American, 7 species belonging 
to our flora and one to Mexico. Z. corollata, including E. paniculata, is the wide-spread and well- 
known representative of this section. The heretofore imperfectly known Michauxian species, £. 
pubentissima and E. mercurialina have been restored by M. Boissier, after a careful examination of 
the original specimens in Richard’s herbarium, now in the hands of Mr. Franqueville of Orleans. 
The former, however, may be a variety of Z. corollata. M. Boissier has from the same source ascer- 
tained that Z. polygonifolia, Michx., is a form of E. Curtisii, though another specimen, in the 
herbarium of the Jardin des Plantes in Paris, is a form of Z. Ipecacuanhe. 
