BOOK REVIEW 



A Monograph on the Genus Heuchera^ 



This monograph, chiefly the work of Dr. Lakela, is a cul- 

 mination of previous treatments of this genus by Dr. Rosendahl, 

 and brings to us a finished review of a most difficult group of 

 plants, interesting especially because of its bicentric distribu- 

 tion in Western America and in the Appalachians. As in Dr. 

 Pennell's admirable treatment of the Scrophulariaceae of east- 

 ern North America, this paper on Heuchera includes full cita- 

 tions of specimens (a necessity for monographic work) , and we 

 look to Dr. Rosendahl and his associates for a similar, compre- 

 hensive treatment of all the Saxifragaceae. Heuchera has ex- 

 panded from 15 species known to Torrey and Gray in 1840 to 

 the 51 species, many with varieties and forms included, treated 

 in this paper. It is wholly a North American genus, most closely 

 related to Boykinia, Sullivantia, and Tiarella, and more remotely 

 to the genera centering about Mitella. Boykinia, with individu- 

 ally closed carpels, is the most primitive of these. As in practi- 

 cally all large genera, many segregations have been previously 

 made, but only the monotypic Conimitella Rydberg {H. Wil- 

 liamsii), and the monotypic Elmera Rydberg {H. racemosa) 

 are maintained. A detailed account (pp. 6-9) of the morphologic 

 units relied upon for taxonomic differentiation: leaves, pubes- 

 cence, floral characters, etc., is accompanied by a full-page il- 

 lustration showing longitudinal flower-sections for each group, 

 delineating especially the angle assumed by the hypanthium 

 with respect to zygomorphy, and affording a better approach 

 to identification of taxonomic sections (and therefore of species) 

 than anything we have had in the past. 



The outstanding interest in this paper, however, is the sec- 

 tion (pp. 15-18) devoted to hybrids of Heuchera. Most of these 

 are hybrids of H. sanguinea. At least one of the cultivated forms 

 is a remarkable bigeneric hybrid (between //. sanguinea and 

 Tiarella), but those of us who have vainly tried to place non- 

 flowering plants of Tiarella within the genus Heuchera are will- 



1 A monograph on the genus Heuchera, Carl Otto Rosendahl, Frederic 

 K. Butters and Olga Lakela. Pp. 1-180, fig. 1-5, 1936. The University of 

 Minnesota Press, Minneapolis, $3.00. 



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