114 CUMMINGS 



tain. It differs from P. coralloides in its stouter branches and lighter 

 color. The thallus is sorediate, with a dull surface, while P. coral- 

 loides is not sorediate and has a shining surface. 



Additional Alaskan species of the genus are : Placodium variabile 

 (Pers.) Nyl., collected at Port Clarence by Dr. Bean, and P. nivale 

 (Koerb.) Tuck., collected by Dr. Bean, but no definite locality given. 

 According to Tuckerman, P. sinapispermum (Auct.) Hepp was col- 

 lected by Wright on the islands of Bering Strait. Nylander, in his 

 revision of Rothrock's list, records P. granulosum Muell., named by 

 Rothrock, as growing on rock on St. Matthew Island, and also states 

 that P. murorum miniatum Tuck., of Rothrock's list, should be named 

 P. elegans tenue (Wahlb.). 



Family COLLEMACE^E. 

 LEPTOGIUM. 



KEY TO THE SPECIES. 



Thallus fringed with white cilia albociliatum. 



Thallus not fringed with white cilia. 



Thallus granulate above myochroum. 



Thallus not granulate above myochroum saturninum. 



13-0. Leptogium myochroum (Ehrh.) Tuck. 



Lichen myochrous EHRHART, Plant. Crypt, n. 286. 1785. SCHAERER, 



Spicil. 534. 1771. SOWERBY, Eng. Bot. t. 1980. 

 Leptogium myochroum TUCKERMAN, Genera 99. 1872. 



Disenchantment Bay (Trelease, 1098/5). A small, sterile frag- 

 ment, perhaps best placed here. 



131. Leptogium myochroum saturninum (Schaer.) Tuck. 



Leptogium saturninum SCHAERER, Spicil. 534. 1840. 



Leptogium myochroum saturninum TUCKERMAN, Syn. N. A. L. i : 166. 1882. 



Muir Glacier (Trelease, 1131); Disenchantment Bay (Trelease, 

 1095, 109 7#). New to Alaska. 



Rhizoids on the under surface poorly developed. 



1 3 2., Leptogium albociliatum Desmaz. 



Leptogium albociliatum DESMAZIERES, Ann. Sci. Nat. iv. 4 : 132. 1855. 



Port Wells, Prince William Sound (Trelease, 1 161). It is recorded 

 by Tuckerman for California and Oregon. New to Alaska. On 

 rocks near tide. 



This is represented only by a very small specimen on which the 

 cilia are not abundant. 



