Periodical Literature. 179 



and are restated again in Harshberger's article on "Bogs," Feb- 

 ruary number of the Plant World. 



Holmboe recognizes ninety species of plants which have been 

 discovered in the bogs of Norway. After a critical study of the 

 remains as found in situ in the peat deposits, Holmboe recog- 

 nizes the following successive strata: (a) dwarf birch, polar 

 willow {Salix herbacea) and water plants; (b) birches (un- 

 doubtedly Betula odorata) which formed the primeval postgla- 

 cial forest, similar to the forest which is represented to-day at the 

 northern limit of trees together with aspen, tall willows, juniper, 

 bilberry, white water-lily (Nymphaea alba) ; (c) pine stratum 

 with alder, hazel, raspberry, twin-flower {Linnaea borealis) and 

 twig- rush {Cladium mariscus) , while in the lowest parts of this 

 stratum with the pine are found remains of dwarf willows and 

 avens {Dry as octope'tala) ; (d) the layer of the oak with the ash, 

 Norway maple, hazel and winter linden {Tilia parvifolia) , these 

 trees being found in a broad belt during the warmest postglacial 

 period, forming in many places extensive forests; (e) the layer 

 of Pinus silvestris (Fichtenzone) which occurs only in a few 

 places in Kristiania and Trondjemsfjord and represents the latest 

 fossil layer of peat; (f) then comes last, the heath stratum char- 

 acterized by the heather {Calluna vulgaris), which exists in great 

 abundance on the treeless west coast of Norway, replacing the 

 earlier forests as the most important formation plant. Similarly 

 K. R. Kupffer found just above the clay bottom of a bog in 

 Russia, a layer of sand ten to fifteen cm. thick, filled with the 

 remains of characteristic alpine plants, such as Dryas octopetala 

 and willows {Salix arbuscula, hastata, herbacea, polaris, myrsin- 

 ites, phylicifolia and reticulata) besides other flowering plants, 

 twenty-eight species in all. 



Europa's Wald in Grauer Vorzeit. Centralblatt f. d. g. Forstwesen, 

 February, 1909, pp. 60-69. 



Bogs, their Nature and Origin. The Plant World, February-March, 

 1909, pp. 34-41; 53-61. 



