Author Institution: Department of Botany and Plant Pathology, The Ohio State University, Columbus 1

Cruden, Robert W.

Fisher, T. Richard

The Ohio Journal of Science

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CHROMOSOME NUMBERS AND OBSERVATIONSIN THE GENUS SILPHIUM'T. RICHARD FISHER AND ROBERT C. CRUDENDepartment of Botany and Plant Pathology, The Ohio State University, Columbus 10Except for three species, a detailed report on the chromosome numbers in thegenus Silphiutn has never been published. During the present study chromosomecounts have been made on over one-half of the species in midwestern and southernUnited States (table 1). Counts and observations were made from micro-sporocytes or root tips smeared in acetocarmine. Voucher specimens are depositedin the herbarium of The Ohio State University.Merrell (1900) reported a chromosome number of n = 8, and 2n = 16 inS. perfoliatum L., although there are uncertainties in his figure 54, which is citedas evidence. Land (1900) merely cited Merrell and reported that 16 appearedto be the number in the embryo sac and 24 in the cells of the endosperm. Taylor(1926), in a more detailed study of the root tips of the same species, consistentlyfound the 2n complement of 14 and was able to show six definite classes ofchromosomes. The present investigation confirms the report of Taylor andrefutes the findings of Merrell and Land. Fisher (1959), in a study describingnatural hybridization between S. terebinthinaceum Jacqs. and S. laciniatum L.,reported n = 7 in the parents as well as in the occasional hybrid.CYTOLOGICAL OBSERVATIONSThe six classes of chromosomes as reported by Taylor (1926) are easily identifiedin root-tip preparations and often during meiosis I (diplotene through diakinesis)according to the relative length, position of kinetochore, and the presence or lackof a satellite. The six classes are:1. length nearly twice as long as the other chromosomes, submediankinetochore2. length slightly over half that of the next longest chromosome, submediankinetochore3. medium length, short arm two-thirds the length of the long arm4. medium length, short arm one-fourth as long as long arm5. medium length, subterminal kinetochore; represented by two pairs6. medium length, subterminal kinetochore with small satellite.All collections examined have n = 7 rather large chromosomes with the exceptionof one collection of 5. trifoliatum L. from Rutherford County, North Carolina.This collection of buds and fruits was made and returned to the research gardenat The Ohio State University in 1957. Some plants of the collection clearly showan extra unpaired chromosome during meiosis. This situation is indicated intable 1 as n = 7 or n = 7+ l .Publication 654, Department of Botany and Plant Pathology. This project supported,in part, by National Science Foundation grant (NSF-G18714) to the senior author.THE OHIO JOURNAL OF SCIENCE 62(5): 258, September, 1962.No. 5 CHROMOSOME NUMBERS IN SILPHIUM 259TABLE 1Documented chromosome numbers of species of SilphiumSpeciesLocation and source ofvoucher material 2nS. asperrimum Hook.S. brachiatum Gatt.S. compositum Michx.5. connatum L.5. dentatum Ell.5. gatesii Mohr.5. integrifolium Michx.S. laciniatum L.S. perfolialum L.5. pinnatifidum Ell.S. reverchonii BushS. simpsonii Greene5. speciosum Nutt.S. terebinthinaceum Jacqs.S. trifoliatum L.Claremore, OklahomaC. B. Heiser 4106Jackson County, AlabamaT. R. Fisher 1776Dinwiddie Co., Va.R. Alston s.n.Jackson Co., N.C.T. R. Fisher 1701Fayette Co., W. Va.Hicks & Bartley s.n.Giles Co., Va.R. Cruden s.n.DeKalb Co., Ga.T. R. Fisher 1759Pickens Co., N. C.T. R. Fisher 1759Martin Co., Ind.R. Cruden 648Coles Co., 111.T. R. Fisher 650Greene Co., Ind.T. R. Fisher 610Coles Co., 111.T. R. Fisher 654Cuyahoga Co., OhioR. Cruden 611Lawrence Co., OhioR. Cruden 575Coffee Co., Tenn.T. R. Fisher 2033Harrison Co., Tex.L. Shinners 24159Jefferson Davis Par., La.L. Shinners 21444Lyon Co., KansasMcGregor 14170Jasper Co., 111.R. Cruden 656Greene Co., Ind.T. R. Fisher 611Madison Co., OhioT. R. Fisher 1690Rutherford Co., N.C.T. R. Fisher S134Fayette Co., W. Va.R. Cruden 6021414LITERATURE CTTEDFisher, T. R. 1959. Natural hybridization between Silphium laciniatum and S. terebinthinaceum.Brittonia 11:250-254.Land, W. J. G. 1900. Double fertilization in Compositae. Bot. Gaz. 30: 252-261.Merrell, W. D. 1900. A contribution to the life history of Silphium. Bot. Gaz. 29: 99-133.Taylor, W. R. 1926. Chromosome morphology in Fritillaria, Alstroemeria, Silphium, andother genera. Am. J. Bot. 13: 179-193.7777777777777777777777+17

Chromosome Numbers and Observations in the Genus Silphium

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Chromosome Numbers and Observations in the Genus Silphium

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