Euphorbia umbellulata Engelm. ex Boissier (1862: 40)

Steinmann, Victor W., 2023, Typification of Mexican Euphorbia (Euphorbiaceae), Phytotaxa 630 (1), pp. 61-68 : 65

Euphorbia umbellulata Engelm. ex Boissier (1862: 40) .

≡ Chamaesyce umbellulata (Engelm. ex Boiss.) Millspaugh (1916: 412) .

Lectotype (designated here):— MEXICO. Jalisco: dry plains east of Guadalajara [‘ad orientem urbis Guadalajara’], 17 May 1849, J. Gregg 856 ( G-DC barcode G00310756 !; isolectotypes F no. 196404 ! [erroneously labeled as “Greeg 826”], GH barcode 00047821 !, K barcode K000253694 !, MO no. 1911423 !, MO no. 1911424 !, NY barcode 00263300 !). Note: Only the isolectotypes at MO have detailed information about the locality and collection date, these apparently transcribed from Gregg’s field notes.

Euphorbia umbellulata is one of many species described by Pierre Edmond Boissier in the first and last monograph of the genus Euphorbia . This small perennial herb is endemic to central Mexico. Boissier cited two collections in the protologue: “In Mexico (Parkinson in herb. Kew!)” and “ad orientem urbis Guadalajara (Gregg n. 856!).” Both of these are complete specimens and representative of the species. The Gregg collection is designated as lectotype because there are six isolectotypes and the collection locality is precise. The Parkinson collection at K (barcode K000253696!) has no further locality information besides Mexico, and the only known duplicate is a scrappy fragment of this specimen removed by Charles F. Millspaugh and now at F (no. 197239!).