Manihot is the genus of cassava, a hugely important tropical staple crop, grown for its starchy roots. Until now, we've had about 6 species represented in our online specimen scans, of the approximately 90-100 known species. Soon we'll have about 60 species represented. The genus is native to South and Central America. It likes dry areas, and most species are found in the cerrados of Central Brazil and in dry areas in Mexico up to the southwestern US, but it's cultivated in wet lowlands also.
It's an odd-looking straggly bush or vine, with leaves that can be simple or lobed or compound on the same plant, and flowers of two sexes that look different from each other. It takes several specimen sheets to represent one species.
In order to put together a collection of specimens to scan, it was necessary to check the recent literature. There's a lot of disagreement about species concepts. The fact that Manihot is cultivated means the cultivars tend to hybridize with the native species when they grow together. Asexual seed production can make it possible for hybrids to stabilize and form new species, making a taxonomic nightmare.
The genus was first monographed in 1971 by Rogers and Appan, who were trying out computer-assisted numerical methods in taxonomy. Antonio C. Allem, of Brazil, followed with many new papers adjusting the taxonomy. I tried to square our Field Museum specimens against the available literature. (Difficult, because even when the authors identified our material, they sometimes changed their minds before they published.) Rogers and Appan deposited many of their original collections at Field, so many scans include their great B&W photos of plants in the field.
We've also added the odd genus Manihotoides (1 Mexican species). It looks like a coca plant with clover leaves.
Rogers & Appan, 1971. Manihot. Flora Neotropica Monographs no. 13.
A.C. Allem. 1979, Rev. Bras. Biol. 39: 735-738; 891-896; 1989. Revision of Manihot sect. Quinquelobae. Rev. Bras. Biol. 49: 1-26; 1999. [descr. of M. baccata], Int. J. Plant Sci. 160: 181-187; 2001. [3 new infraspecific taxa & new synonyms], Novon 11: 157-165.