THE NORTH AMERICAN SPECIES OF ASTERELLA. 
By ALEXANDER W. EVANS. 
INTRODUCTION. 
The genus Asterella was published by Palisot de Beauvois, prob- 
ably in 1805,1 and was based on the two Dillenian species, “ Lichen 
pileatus parvus carinatus, capitulis fimbriatis ” and “ Lichen pileatus 
parvus, foliis crenatis.”? In the first edition of his Species Plant- 
arum (1753) Linnaeus had recognized both of these species and had 
included them in his composite genus J/archantia, giving them the 
binomial names M. tenella and M. hemisphaerica. Palisot de Beau- 
vois accepted these specific names and designated his two species 
Asterella tenella and A. hemisphaerica. According to modern ideas 
the genus as originally defined was a composite, its two species no 
longer being considered congeneric. In spite of this fact it was ade- 
quately published and deserves recognition in a restricted sense, if 
the current rules of nomenclature are followed. Botanists, however, 
persistently ignored its claims for over 50 years, and many refuse to 
admit their validity even at the present time. This is due partly to 
the confusion caused by Lindberg and Trevisan in their attempts to 
reestablish the genus and partly to the fact that two other genera, 
proposed for the reception of the Linnaean Jf. tenella and M. hemi- 
sphaerica, had come in wide use. 
The genera in question are Reboulia and Fimbriaria. Reboulia was 
published by Raddi in 1818° and was based on M. hemisphaerica; 
Fimbriaria was published by Nees von Esenbeck in 1820‘ and in- 
cluded M. tenella and three other species. If Raddi had known of 
Palisot de Beauvois’s genus and had recognized its composite nature, 
the establishment of a new genus upon either of its component species 
1ZLam. Dict. Sci. Nat. 3: 257. 1805 (?). This citation has been kindly sup- 
plied by Dr. John Hendley Barnhart, of the New York Botanical Garden. Dr. 
Barnhart states that the date is somewhat doubtful but that the volume cited 
could not have been published later than 1806. 
2 Hist. Muse. 521. pl. 75, f. 43 519. pl. 75, f. 2. 1741. 
*Opuse, Sci. Bologna 2: 357. 1818. The name was originally spelled 
“ Rebouillia.” 
*Hor. Phys. Berol. 44. 1820. The name was originally spelled “ Fimbraria.” 
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