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THE AMERICAN NATURALIST [Vol. XLV 



istence of several distinct laciniate forms of different 

 species of trees and shrubs. The varieties heterophylla, 

 laciniata, asplenifolia 45 and incisa of Fagus sylvatica, 

 Alnus glutinosa laciniata, A. glutinosa quercifolia and A. 

 glutinosa oxyacanthifolia are instances to which numer- 

 ous others might be added. It would seem that the 

 laciniate forms of Mercurialis annua, observed by 

 Marchant, would find a place here. 40 



The repeated sudden appearance of the same variety 

 has been noted by various authors. Darwin, Korschin- 

 sky, 47 the late director of the St. Petersburg Botanic 

 Garden, and de Vries 48 give numerous instances. Thisel- 

 ton Dyer was able to show the repeated formation of at 

 least two new varieties of Cyclamen latifolium. 49 Many, 

 from personal experience, will be able to supply other 

 instances. And while most of the cases which come to 

 our notice probably are explainable through accidental 

 transportation of seed or through Mendelian splitting of 

 a hybrid between the species and a retrograde variety or 

 through atavism, 50 there are others which do not admit 



45 This variety, like cut-leaved varieties of other species, not infrequently 

 shows atavism in certain shoots. See de Vries, "Atavismus durch Samen 

 und durch Knospen" (" Mutationstheorie, ' ' 1: 482), and also E. G. 

 Leavitt, "Partial Eeversion in Leaves of the Fern -leaved Beech," Bhodora, 

 6: 45, 1904; O. Paulsen, "Blivende Axelblade hos Boegen," Bot. Tidskr., 

 24: 281, 1902; A. Trotter, "Contributo alia teratologia vegetale," S. S. 

 Bot.^ Italy, 44, 1902.^ 



believe generally is done— laciniation to be a "unit-character" it would 

 seem that such a "unit-character" may be subject to considerable varia- 

 tion, though the degree of variation is constant or at least approximately 

 so for each individual case. This relative stability of the varietal character 

 of course does not prevent the extremes of each degree of variation from 

 overlapping. 



" Korschinsky, S., " Heterogenesis und Evolution," Flora, 89, 240, 1901. 

 ""Species and Varieties," 627. 



"Thiselton Dyer, W. T., "The Cultural Evolution of Cyclamen lati- 

 folium," Proc. Roy. Soc, 61: 135, 1897. See also J. Denman, "The 

 Sporting Peculiarity of the Persian Cyclamen," Gard. Chron., 3d Ser., 



