THE BHYOPHYTA OF ICEI.AM) 497 



cortex in this species consisls of 3—4 lavers of sharply defined, small 

 stereids covered with a sphagnoid outer corlex, while P. f'onlana has not 

 a sharply diflerentiated cortical laver. This feature appears, however, 

 to be closely connected with the degree of dampness of the habitat, so 

 that forms from a dry substratum, both of P. lomentellii and of P. fon- 

 taiia. have several laN-ers of thick-walled cortical cells, while bog-forms 

 have thin-walled cortical cells, and (as in Dicraiuim acojmrium and D. 

 anqnslnm) all possible transitions ma\' be found betwcen thin-walled and 

 thick-walled cortical cells. 



Fr.uit occurs very frequently and ripens at the end of .luly or in 

 the beginning of August. 



Fam. TIMML\CEÆ. 

 192. Timmia norvegica Zett. 



E. Iceland: Hofl; Vallanes (H. J.)!. N. Iceland: Pollar (St.)!; Akureyri!, 

 at an attitude of 300 metres; Hof near Eyjafjordur O. D.)I; Vidimvn 

 (Grl.)!. S. Iceland: Vestmannaey !. 



It grows on earth and in rock-clefts, but has been collected everj'- 

 where only scantily. Near Hof (^E. Iceland) it grew on gravelly ground 

 in association with Oncophonis virens. Diirichnm flexicaiile, Mijiirella 

 jnldcea and M. apiciilata at an attitude of about 150 metres. Near 

 Akureyri it was found sometimes in rock-clefts, in company with Mnium 

 orthorrhijnchiim, sometimes on rocks mixed with Philonotis tomentelht. 

 Only sterile specimcns have been found. 



193. Timmia austriaca Hedw. 



Very common especially in N. and E. Iceland, but more rare in 

 NW. Iceland (D\rafj6rdur, Isafjordur, Grunnavik!). It grows on earth 

 or on soil-covered rocks, and often in masses. Thus in several piaces 

 in Hallormstadaskogur it was the most abundant member of the moss- 

 carpet under the birches. especially on knoils and soil-covered stones. 

 In several piaces in X. Iceland. for instance in Oxnadalur, it covered 

 the slopes along streams, often greatly mixed with other species. 



Timmia (lustriaca is most froquent in the lowlands up to a height 

 of about 300—400 metres, but is also often found on mountain heights 

 (for instance on Seljaland at an attitude of about 620 metres) although 

 usually in small quantity. Fruit has been found only near Tvera and 

 Vidim\ri in X. Iceland; it occurred plentifully in both piaces and had 

 just ripened at the end of July. 



Fam. POLYTRICHACEÆ. 



194. Catharinea undulata (L.) Web. 



E. Iceland: Hornafjordur! ; LonI; Berufjordurl. X. Iceland: Hof near 

 Eyjafjordur (O. D.j!; Reykir near Svinavatn Grl.)!. W. Iceland : Reykja- 



