THE BRYOLOGIST 



Vol. XX September, 1917 No. 5 



THE GENUS PARMELIOPSIS OF NYLANDERi 



Lincoln W. Riddle 

 (With Plate XX) 



The writer's interest in the group of lichens to be discussed in this paper 

 was first aroused by collecting from an old fence in Needham, Massachusetts, 

 a small, gray, foliose lichen, densely covered with isidia, and suggesting Parmelia 

 rudecta Ach., but lacking the white punctations of that species. In subsequent 

 collecting the lichen was found to grow also on the bark of pines, and proved 

 to be common in Massachusetts, although apparently not much collected. A 

 comparison with material in the Tuckerman Herbarium showed that the plant 

 was what he had called Cetraria aleurites (Ach.) Th. Fr. But when the European 

 authorities were consulted, it was found that there was much confusion in their 

 interpretation of the Lichen aleurites of Acharius. Visits to the leading European 

 herbaria in 1912-1913, including the original herbarium of Acharius now in the 

 Botanical Museum at Helsingfors, gave an opportunity to study first hand the 

 problem of Lichen aleurites and its allies. 



These lichens have been known by American students under the names 

 used in Tuckerman's "Synopsis of North American Lichens": Cetraria aleurites, 

 Cetraria aleurites var. placorodia, Parmelia ambigua, and Parmelia amhigua var. 

 albescens. Tuckerman thus considered two of these to be varieties of the other 

 two, but most authors hold the view that there are four distinct species, and as 

 will be shown later there are actually five recognizable forms. A glance at the 

 synonymy cited below under the species aleurites will show how various have 

 been the ideas in regard to the affinites of this plant. Furthermore, although 

 Tuckerman and others have distributed these lichens between two genera, they 

 are closely related, this close relationship leading to the confusion which has 

 existed in regard to the names. 



For this group of species, Nylander in 1861 (Lichenographia Scandinaviae, 

 p. 105) proposed the name Parmeliopsis as a section of the genus Parmelia. Five 

 years later (Lichenes Lapponiae OrientaHs in Not. Sallsk. pro F. et Fl. Fenn. 

 Forh. n. s. 5: 121) he established Parmeliopsis as a genus with Lichen ambiguus 

 Wulfen as the type-species; and he continued this treatment of the group in 

 the part of the second volume of his Synopsis Lichenum (page 53) published 

 in 1888.2 



^Read at the December, 19 16, meeting of the SuUivant Moss Society, New York City. 



'This part of the Synopsis Lichenum bore no date. The date of publication as given by 

 various authors varies considerably. I am adopting the date given by the Abbe Hue, who should 

 certainly have been in a position to know. 



The July number of the Bryologist was published August 15, 1917. 



