Frondescence and Fasciation. 185 



responsible for virescence of Trijolium procumbens, * and of 

 Trifolium arvense. f 



The virescence of certain of the individual flowers of our 

 Taraxacum evidently was not as pronounced as that of the 

 plants mentioned by Pluskal, * * for he calls especial attention 

 to the infertility of the flowers. The Ann Arbor specimen how- 

 ever produced abundant seed, which was sown and \ ielded 

 some eighty or ninety plants which up to the present have not 

 flow^ered. From the results obtained we will be able to judge 

 in a year or two whether this abnormal form is entitled to 

 varietal rank. And while, a priori, we would not be inclined 

 to take this view, it must be remembered that cases of vires- 

 cence are known where not only the virescence reappears vear 

 after year, as in the strawberry f f.but that the virescence may 

 be transmitted through the seed as in the case of Oxalis stricta 

 viridiflora. In neither of these instances, certainly not in 



the last, the virescence appears to be of a pathological character. 

 Other instances of virescence are known which could be ascribed 

 to other organisms, plants or animals, as in the instances above 

 quoted. Peyritsch|| has shown that by transferring aphids 

 from virescent to healthy plants, virescence may be induced. 

 A third kind of virescence, of which the cause never was ascer- 

 tained, has been known to assume the proportions of an epi- 

 demic which may last for years. 



The second frondescent specimen of our Taraxacum enabled 

 us to carry on experiments to determine the inheritance. It 

 is rather expected that during the next year other such speci- 

 mens will be found, for though the two described were the first 

 we encountered, similar specimens have been noted before 

 as shown by by the instances given above. A remarkably good 

 specimen of this character appears to have been the one referred 



*Schlechtendahl, H. ^R. von., Uebcrsicht der Ph> toptocecidien. Zeitschr. f. Naiurw. 

 55: 1882. 



tKalepa, A,, Neue Arten der Gattung Phytoplus und Cecidophyes. Densch. k. k. 

 Akad. d. Wiss. 59 525. 1893. 



• *Pluskal. F S.. Beitrage zur Teratologic und Pathologie der Vegetation. Oest. Bot. 

 Wochenbl. 2: 371. 1852. I'nfortunately I am unable to find Bruhin.s " Xeue Beitrage" 

 which contains the original description of an abnormality similar to the one figured here 

 and to which reference is made in his "Teratologische Beitrage," in Verh. k. k. zool. 

 bot. Gesell. Wien. 17: 97. 1876. 



t fHolmes, Plymouth Strawberry. Gard. Chron. 3rd Ser. 30: 58. 1901. 



|Hus, H.. Virescence of Oxalis stricla. Ann. Rep. Missouri Bot. Garden. 18: 99. 



PI. 10, 11. 1907. The distinction between virescence and frondescence shoule be kept 



in mind. 



llPeyritsch, J., Zur Aetiologie der Cholranthein einiger Arabisarten. Jahrb. f. wiss. 



Bot. 13: .1 1882. 



1 I |De Vries, H., Een epidemic van vergrocningen. Bot. Jaarb. Dod. 8: 66. 1896. 



