444 BIOGRAPHICAL SKETCHES. 
Thus his first monograph was of the genus Cuscuta (pub- 
lished in the American Journal of Science, in 1842), of which 
when Engelmann took it up we were supposed to have only 
one indigenous species, and that not peculiar to the United 
States, but which he immediately brought up to fourteen 
species without going west of the Mississippi Valley. In the 
year 1859, after an investigation of the whole genus in the 
materials scattered through the principal herbaria of Europe 
and this country, he published in the first volume of the St. 
Louis Academy of Sciences a systematic arrangement of all 
the Cuscutw, characterizing seventy-seven species, besides 
others classed as perhaps varieties. 
Mentioning here only monographical subjects, we should 
next refer to his investigations of the Cactus family, upon 
which his work was most extensive and important, as well as 
particularly difficult, and upon which Dr. Engelmann’s author- 
ity is of the very highest. He essentially for the first time 
established the arrangement of these plants upon floral and 
carpological characters. This formidable work was begun in 
his “Sketch of the Botany of Dr. A. Wislizenus’s Expedition 
from Missouri to Northern Mexico,” in the latter’s memoir of 
this tour, published by the United States Senate. It was fol- 
lowed up by his account (in the American Journal of Science, 
1852) of the Giant Cactus on the Gila ( Cereus giganteus) 
and an allied species; by his synopsis of the Cactacee of the 
United States, published in the “‘ Proceedings of the American 
Academy of Arts and Sciences,” 1856; and by his two illus- 
trated memoirs upon the southern and western species, one 
contributed to the fourth volume of the series of Pacific Rail- 
road Expedition Reports, the other to Emory’s Report on the 
Mexican Boundary Survey. He had made large preparations 
for a greatly needed revision of at least the North American 
Cactacee. But, although his collections and sketches will be 
indispensable to the future monographer, very much knowledge 
of this difficult group of plants is lost by his death. 
Upon two other peculiarly American groups of plants, very 
difficult of elucidation in herbarium specimens, Yucca and 
Agave, Dr. Engelmann may be said to have brought his work 
