100 The Ohio Journal of Science [Vol. XVII, No. 3, 



extrusion; this phenomenon occurs extensively in T. IcEvigatnm, 

 and has been found in material so carefully prepared and in 

 such well-defined stages that its genuineness cannot be brought 

 into question. This phenomenon apparently was not observed 

 by Osawa" as contributing to the pollen abnormalities of T. 

 albidiim. As found in T. Icevigatum, this extrusion takes the 

 form of a centrifugal wandering of granules of stainable material 

 and their speedy organization into accessory nucleii so soon as 

 they pass through the parental nuclear membrane. 



Finally, the occurrence of diads, as before mentioned, is due 

 to entire loss of the reduction division — the mother cell dividing 

 once and both daughters forming into "pollen-grains." 



In neither of the species studied is the chromosome count 

 any lower than in any sexual species for which it has been 

 taken, as is generally true for the amiotically parthenogenetic 

 species of Taraxacum that have been investigated. Moreover, 

 both species possess such a wide range of forms that the only 

 safe criterion for separating them seems to be achene color and 

 form. While this polymorphy may be correlated with what 

 seems to be an unwieldy chromatin content — so far as the 

 reproductive cells are concerned — nevertheless, when taken in 

 conjunction with the observed pollen abnormalities and the 

 chromosome count it points strongly toward hybridism, 

 possibly quite complex hybridism, as an explanation. That 

 this idea has the specific sanction of Blaringhem^ and others 

 is well known. However, I do not wish to be understood as 

 asserting that such evidence can ever prove the existence of 

 complex, or even simple, hybridism, as some workers undoubt- 

 edly believe. 



BIBLIOGRAPHY. 



(Containing only important papers to which specific reference is made). 



1. Handcl-Mazetti, H. Freih. V. Alonographie der Gattung rflra.racHW. Leipzig 



und Wien. 1907. 



2. Raunkiaer, C. Kimmdanelse nden Befrugtning lios Moll-cebotte. Kjobenhavn, 



Bot. Tidssknft 25: 109-140. 1903. 



3. Kirschner, O. Parthenogenese bei Bkitenpflanzen. Jaliresl). d. Ver. f. vaterl. 



Naturk. in Wurtemburg. 1900. 



4. Tuel, O. Die Tetradenteilung an der Samenanlage von Tdnixacum. Ark. f. 

 " Bot. 2, No. 4. 1904. 



5. Schorbatow, L. Parthenogenese imd apogame Entwicklung bei den Bkiten- 



pflanzen. Entwicklungsgeschichtliche Studien an Taraxacum officinale \\'igg. 

 Trav. Soc. nat. Univ. imp. Kharkhow 45: 15-55. 1911-12. 



6. Winkler, H. Parthenogenesis und Apogamic in Pflanzenrcich. Prog. Rei Bot. 



2, No. .3: 293-454. 1908. 



7. Osawa, J. Studies on the cvtologv of some species of Taraxacum. Arcli. f. 



Zellforschung 10: 4.50-469. '1913. 



8. Blaringhem, L. Remarques sur la parthenogenese des vegetaux superieurs. 



C. R. Seanc. Soc. BioL dc Paris 6(5: 507-508. 1908. 



Date of Publication, January 20, 1917. 



