The Variations of Polygonum Punctatum

Abstract

This study is based primarily on material in the following herbaria: Cranbrook Institute of Science (BLH); Chicago Natural History Museum (F); Gray Herbarium (GH); Herbario Nacional del Instituto de Biologia de la Universidad Nacional de Mexico (MEXU); Missouri Botanical Garden (MO); New England Botanical Club (NEBC) ; New York Botanical Garden (NY); Oberlin College (OB); Herbarium of the University of Pennsylvania (PENN); University of Texas (TEX); University of California Herbarium (UC); Herbarium of the University of Wisconsin (WIS). Relatively few of the herbarium sheets have been cited; the standard abbreviations given above in parentheses have been used to designate the location of each. The writer wishes to express his appreciation for loans from most of these herbaria. Herbarium material has been augmented by several mass collections, discussed in Part V; most of these were made during travel supported in large part by the Wisconsin Alumni Research Foundation. I am also indebted to my colleagues, Prof. C. L. Huskins and Dr. Robert Duncan, for reading the manuscript and making several suggestions. Figure 19 is based on a map prepared by Prof. V. C. -Finch, and the others on Hall's Outline Maps and Graphs, No. 205C. Polygonum punctatum Ell. ( P. acre HBK') is a well-marked species, ranging from southern Canada to Argentina. It shares with P. Hydropiper the characteristic feature of having glandular dots2 on the perianth; it differs from P. Hydropiper primarily in having smooth and shining, rather than roughened and dull, achenes, and in strong. tendencies toward longer internodes, less drooping spikes, and less red coloring in the perianth. In spite of the clarity of these characters, most herbaria have a remarkable assemblage of species under the name P. punctatum or P. acre, including not only P. Hydropiper but such species as P. hydropiperoides, P. lapathifoliuwm, etc. Hybridization within the Persicari# group does not seem to be common, considering the tendency for many closely related species to grow together. Cursory studies of several mass collections, made by taking at random many individuals of all species of the Persicaria group growing in a limited area, have yielded very few individuals not clearly put into one species or another. In the course of annotating material from 5 herbaria, some 1233 sheets were labelled as being some phase of P. punctaturm, while 7 were found to combine the dull achenes of P. Hydropiper with the long internodes of P. punctatum. These collections, presumably representing hybrids between the two species, are as follows: NOVA SCOTIA: Louisberg, Cape Breton Island, July 19, 1889, Macoun 20199 (NY). NEW JERSEY: Watchung, Somerset Co., Aug. 8, 1930, Moldenke 1357, and Sept. 15, 1934, Moldenke 8288 (NY). VIRGINIA: Queens Creek at Capitol Landing, Aug. 22, 1921, Grimes 4306 (GH). WISCONSIN: New London, Sept. 13, 1931, Fassett & Rhodes 13170 (WIS); East Troy, Walworth Co., Aug. 2, 1928, Almon (WIS).