The North American Species of Placynthium
Henssen A. 1963. The North American Species of Placynthium. Canadian Journal of Botany. 41(12):1687-1724
ABSTRACT: A general survey is given of the morphology and anatomy of the genus Placynthium. The species: aspralile, flabellosum, nigrum incl v. tantaleum, petersii, subradiatum, and stenophyllum are described in detail. The following new combinations are made: Placynthium filiforme, Placynthium aspralile, Placynthium subradiatum f. coerulescens, and Synalissa subnigra. The new variety Placynthium stenophyllum v. isidiatum is established.