1911] Robinson, — Notes on the Genus Cirsium 239 
extenuation that during the rather brief interval between the publi- 
cation of the International Rules of Nomenclature in 1906 and the 
beginning of presswork on the Manual in 1907 it was necessary for 
the editors to re-examine some thousands of botanical names, already 
in the manuscript, and to revise them in accordance with a new series 
of rules. It is therefore not remarkable that in a group where syn- 
onymy is especially complicated Carduus spinosissimus Walt. was 
confused with the specific homonym Cirsium spinosissimum Scop. 
Had time permitted a more careful study of the literature involved, 
it would have been evident that Cirsium spinosissimum Scop. was 
founded upon Cnicus spinosissimus L., a distinct species of central 
Europe. 
There being this valid and earlier specific homonym, Cirsium 
spinosissimum (L.) Scop. Fl. Carn. ed. 2, ii. 129 (1772), it is clear 
that the specific name used by Walter in his Carduus spinosissimus 
(1788) cannot be revived to replace Cirsium horridulum Michx. Fl. 
Bor. Am. ii. 90 (1803). Our common yellow-flowered thistle should 
therefore be called, as formerly, Cirsium horridulum Michx., a fact 
duly recognized by the recent Cirsium specialist Petrak, Bot. Tidsk. 
xxxi. 58 (1911). 
It is hoped that users of the Manual will note this correction, so 
that the unfortunate error may not lead to further confusion. 
As the name Carduus spinosissimus Walt. has of late been pretty 
generally adopted by those who employ the American rules of nomen- 
clature, it may be worth while to call attention to the fact that this 
name seems to be invalidated under the Madison amendments of the 
Rochester Code, since there is clearly an earlier congeneric homonym 
in Cnicus spinosissimus L. I am not sure whether these Madison 
amendments are now considered valid, but in any event I fail to see 
how Carduus spinosissimus Walt. can be employed in the same work 
with Chrysopsis pilosa (Walt.) Britton and Chrysopsis Nuttallii 
Britton,— names illustrating a parallel case inversely treated. 
While speaking of the genus Cirsium I may here record the follow- 
ing transfers, which it has seemed necessary to employ in the rearrange- 
ment and labelling of material in the Gray Herbarium. 
Cirsium americanum (Gray), comb. nov. Echenais carlinoides, 
var. nutans Gray, Proc. Acad. Philad. 1863, p. 69, not DC. Cnicus 
carlinoides, var. americanus Gray, Proc. Am. Acad. x. 48 (1874). 
Cnicus americanus Gray, Proc. Am. Acad. xix. 56 (1883). 
