Author Institution: Department of Biological Sciences, Kent State UniversityThe water smartweeds are now considered one species, Polygonum amphibium sensu lato, represented in the Ohio flora by two varieties. One, var. stipulaceum, occurs mainly in the glaciated portion of Ohio; the other, var. emersum and also the intermediates between these two varieties, have an apparent random distribution in the state

Hobbs, Clinton H.

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BRIEF NOTEDistribution of Polygonum amphibium L. (Polygonaceae) in OhioCLINTON H. HOBBS, Department of Biological Sciences, Kent State University, Kent, OH 44242ABSTRACT. The water smartweeds are now considered one species, Polygonum amphibium sensu lato, rep-resented in the Ohio flora by two varieties. One, var. stipulaceum, occurs mainly in the glaciated portion ofOhio; the other, var. emersum and also the intermediates between these two varieties, have an apparent ran-dom distribution in the state.OHIO J. SCI. 89 (3): 65-66, 1989The Ohio water smartweeds have borne various Latinnames such as Polygonum amphibium L., P. natans Eaton,P. coccineum Muhl., P. fluitans Eaton, P. hartwrightii A.Gray, P. inundatum Raf., and P. mublenbergii S. Watson.However, they have generally been placed in two species,as by Fernald (1950), Gleason (1952), and Weishaupt(1971), differentiated primarily by the length and thick-ness of the inflorescence. Fernald identifies the first spe-cies as P. amphibium with inflorescences 1-4 cm longand 1-2 cm thick, while the second species is identifiedas P. coccineum with inflorescences 4-18 cm long and 7-1 5 mm thick. Gleason determines the first species asP. natans with inflorescences 1-3 (rarely 4) cm long andIVi cm thick, while the second species, determined asP. coccineum, has inflorescences 4-15 cm long and about1 cm thick. Weishaupt uses the same nomenclature asFernald but separates the two species on the basis of in-florescence length only, using 4 cm as the critical divid-ing point. Specimens are commonly encountered whichdo not fit well in either species. One problem has beenthat emergent or terrestrial shoots differ markedly inmorphology from aquatic shoots. The three authors re-ferred to above consider that each species has bothaquatic and terrestrial forms.Mitchell (1968, 1978) grouped the whole assemblageinto one species, Polygonum amphibium, placing themost hydrophytic American plants in var. stipulaceumColeman, and the least hydrophytic plants in var. emer-sum Michx. (Polygonum amphibium var. amphibium is pri-marily European). The American plants in this species"appear to represent a cline of phenotypic variabilityfrom the most amphibious to the least. This corre-sponds to a morphological gradient with var. stipulaceumat one end, var. emersum at the other, and a broad rangeof intermediates" (Mitchell 1978).The following key to the varieties delineates the chiefmorphological differences.a. Plants aquatic or terrestrial; inflorescences whenpresent 4 cm long or less; leaves lanceolate or ellip-tic, acute or obtuse; stipules flanged or notvar. stipulaceumb. Plants aquatic, flowering; leaves glabrous, el-liptic, acute or obtuse at apex; stipules notflangedaquatic phase (Fig. 1C)aa.bb. Plants terrestrial, not flowering; leavespubescent, lanceolate, attenuate but notacuminate at apex; stipules flanged.. terrestrialphase (Fig. IB)Plants terrestrial; inflorescences 4-15 cm long;leaves ovate-lanceolate, long-acuminate; stipulesnot flanged var. emersum (Fig. 1A)To be placed in Mitchell's third category, "varietalintermediates," plants with attenuate leaves and flangedstipules would have to be flowering. Likewise aquaticplants would have cordate leaves rather than elliptic(Fig. ID). There are other combinations of charactersuntypical of the two varieties which would result in theplant's being placed with the varietal intermediates.'Manuscript received 1 September 1988 and in revised form12 January 1989 (#88-l4BN).FIGURE 1. Representative leaves of Polygonum amphibium L.: A. P.amphibium var. emersum; B. P. amphibium var. stipulaceum terrestrialphase; C. P. amphibium var. stipulaceum aquatic phase; D. one ex-ample (aquatic) of "varietal intermediate" between var. emersum andvar. stipulaceum.66 C. H. HOBBS Vol. 89Ohio water smartweeds were studied in herbaria ofthe following 19 institutions: Baldwin-Wallace College,Bowling Green State University, Cleveland Museum ofNatural History, Dayton Museum of Natural History,Denison University, Heidelberg College, Kent StateUniversity, Miami University, Muskingum College,Oberlin College, Ohio State University, Ohio Univer-sity, Ohio Wesleyan University, University of Akron,University of Cincinnati, Urbana University, Wilming-ton College, Wittenberg University, and YoungstownState University. Using Mitchell's scheme, these speci-mens were classified in the three taxonomic categoriesby visual inspection. This was easy to do using the keygiven above, as the differences were fairly obvious. Thecounty distribution of documented specimens of thethree taxonomic categories is listed in Fig. 2.As may be noted from the map, the variety stipu-laceum occurs least frequently — in 16 counties, all ofthem glaciated except Coshocton County. The varietyemersum in 60 counties and the varietal intermediates in37 counties appear to have random distribution in thestate. In general, P. amphibium var. stipulaceum has amore northerly range in the United States and Canada,which is the area that was glaciated. P. amphibium var.emersum (P. coccineum in most current manuals), on theother hand, has a more southerly range. Thus, Deam(1940) in Indiana and Wherry et al. (1979) in Pennsyl-vania show var. stipulaceum confined to northern, glaci-ated counties. Voss (1985) in Michigan shows var.stipulaceum occurring farther north in the state than var.emersum. Radford et al. (1964) report var. emersum occur-ring, but rare, in North Carolina and South Carolina,while var. stipulaceum does not occur in these southernstates.ACKNOWLEDGMENTS. I thank the curators of the herbaria namedabove for their kind assistance, and my colleague, Dr. Tom S.Cooperrider, for helpful suggestions on the manuscript of this paper.LITERATURE CITEDDeam, C. C. 1940 Flora of Indiana. Department of Conserva-tion, Division of Forestry, Indianapolis, Indiana. 1236 p.Fernald, M. L. 1950 Gray's Manual of Botany. 8th Ed. Ameri-can Book Co., New York, New York. 1632 p.Gleason, H. A. 1952 The New Britton and Brown illustratedflora of the northeastern United States and adjacent Canada.Vol. 2. New York Botanical Garden, New York. 655 p.Polygonum amphibium-• var. stipulaceum•- var. emersum* intermediatesFIGURE 2. Documented Ohio distribution of Polygonum amphibiumvarieties and intermediates.Mitchell, R. S. 1968 Variations in the Polygonum ampbibium com-plex and its taxonomic significance. Univ. Calif. Publ. Bot. 45:1-65.Mitchell, R. S. and J. K. Dean 1978 Polygonaceae (BuckwheatFamily) of New York State. New York State Museum BulletinNo. 431. Albany, New York.Radford, A. E., A. E. Ahles, and C. R. Bell 1964 Manual of thevascular flora of the Carolinas. University of North Carolina Press,Chapel Hill, North Carolina. 1183 p.Voss, E. G. 1985 Michigan Flora. Part II. Cranbrook Instituteof Science and University of Michigan Herbarium. Ann Arbor,Michigan. 724 p.Weishaupt, C. G. 1971 Vascular plants of Ohio. 3rd ed. Kendall/Hunt Publishing Co., Dubuque, Iowa. 292 p.Wherry, E. T., J. M. Fogg, and H. A. Wahl 1979 Atlas of theFlora of Pennsylvania. Morris Arboretum of the University ofPennsylvania, Philadelphia, Pennsylvania. 390 p.

Brief Note  Distribution of Polygonum amphibium L. (Polygonaceae) in Ohio

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Brief Note Distribution of Polygonum amphibium L. (Polygonaceae) in Ohio

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