Fillk: LICHENS OF THE NORTHERN BOUNDARY. 179 



The first genus shows a good cortex on all sides of the fruticose 

 thalli, but the plants, rising from the substratum, need such pro- 

 tection even in the shaded habitat. The Collcmaoi course has 

 no cortex and is a shade and moisture loving plant -par excel- 

 lence. The members of the last genus have a poorly developed 

 cortex and are nearly as strictly ombrophytic as the Collema. 

 The Cladonia and the Bceomyces show podetia protected by a 

 good cortex, so that they rise easily from the substratum. The 

 single Biatora has a thallus consisting merely of a tangle of 

 epilithic algal cells and fungal hyphae and is as strictly confined 

 to shaded habitats as is Pannaria languinosa (Ach.) Kbr. The 

 Peltigeras have a good cortex above, and the abundant rhizoids 

 of lower layer horizontally disposed hyphas serve well enough for 

 protection to the lower side of such shade or moisture loving 

 plants as the members of the genus commonly are. Other 

 members of the formation need no further mention than the state- 

 ment already made that they have a good cortex on both sides 

 and are not so strictly ombrophytic. 



In considering the more familiar formations first, we shall 

 now pass from the rock lichens to those of trees, and these may 

 be passed over with a brief statement. These formations have 

 been duly considered in the fifth and sixth papers of this series, 

 and nothing would be added by giving space to long lists of 

 species ; nor is it thought necessary to repeat the statements re- 

 garding adaptations as already given in the sixth paper. Briefly 

 then, regarding the Par melia formation of trees with rough 

 bark as studied in a number of localities, the only new plants 

 of such formations noted in any of the localities were Ramalina 

 ■pusilla (Prev.) Tuck., Cetraria juniferina (L.) Ach. var. -pin- 

 astri Ach., Alectoria jubata (L.) Tuck, and Parvielia conspur- 

 cata (Schaer.) Wainio. These are partly plants not found in 

 the regions farther south, too rare to include in the formations 

 or found growing in slightly different relations and not included. 

 Reviewing next in order the Pyrenula formation of trees with 

 smooth bark, the additional plants are Lecanora variolascens 

 (Fr.) Nyl., Lecanora verrucosa (Ach.) Laur. var. mutabilis Th. 

 Fr., Biatora varians (Ach.) Tuck, and Biatora atropurpurea 

 (Mass.) Hepp. ; and all of these plants were found in one or both 

 of the regions discussed in the papers mentioned above, but either 

 were rare or not present at the places where the formations were 

 studied. These formations were noticed more at Emo than 



