MICROPALAONTOLOGY OF POSTGLACIAL DEPOSITS. 455 
3. Detritus-Gyttja—A dense, more or less elastic substance, without 
phyto-structure in the matrix, but often traversed by rootlets of Phragmites 
and Equisetum. The colour is brown, usually tinged with green of different 
shades. In the air it darkens rapidly, but, upon drying, the colour usually 
revives a little. Alkaline extract green or slightly brownish. 
4. Lake Dy (Swed. *sjódy").—4A dense substance, usually but slightly elastic, 
without phyto-structure in the matrix. The colour is brown or brownish 
black, with usually a slight tinge of green. It blackens rapidly in the air, 
and does not brighten, or searcely brightens, upon drying. Alkaline extract 
a decided brown colour. 
5. Lime-Gyttja.— A dense, usually clastic substance without phyto-structure 
in the matrix, but as a rule rich in shells of freshwater snails and mussels. 
The colour is whitish-yellow, reddish-yellow, yellow-brown, or of various 
greenish tints, often mottled. When heated with acid, it bubbles and hisses 
slightly. 
In places Lewis speaks of “recent peat” without any accurate definition 
of the term. It would be better not to speak of “recent peat’’ at all, 
because it must always be doubtful where the boundary between recent and 
not recent is to be drawn. “ Recent” is a term which it is only permissible 
to apply to the vegetation still growing on the surface of a peat moss. We 
may define as “ sub-recent " material belonging to the “ forna” [ Hesselman, 
1911; Sernander, 1918 = humus nekron; cf. also Moss, 1904, fig. 6; 
Lewis, 1904, p. 321; Paul, 1916 (* Latsehenhumus?"); Ramann, 1918, 
p. 70; C. Weber, 1903, p. 430 (“Streudecke ”)] if we are dealing with 
sedentary deposits, or material belonging to the “äfja” (Sern. l. c. =sapropel 
nekron) if we are dealing with sedimentary deposits. The term “ sub-fossil ” 
is not needed, as there is no reason why peat, pre-, inter-, and post-glacial, 
should not be called fossil. Some authors, indeed, apply the term sub-fossil 
to all remains found in postglacial deposits (cf. Paul, 1924) ; others only 
to those found in the Atlantic layers. 
In a recent paper, Rigg (1922) describes a bog forest in the neighbourhood 
of Victoria, British Columbia, with lodgepool pine (Pinus contorta) dominant, 
Labrador tea (Sedum grænlandieum), Shallon (Gaultheria Shallon), etc. These 
species are constituents of the recent vegetation. The floor of the pine forest 
is thickly covered with pine-needles mixed with a small amount of other 
material of vegetable origin. Under the surface decay has begun. The 
depth of the layer of pine-needles in various stages of decay is from 6 to 
12 inches. This is the “ fórna-layer," or the sub-recent material, which often 
plays an important part in the forming of peat. Beneath this is a layer of 
old Sphagnum peat, usually 12 inches or more thick (= the fossil material). 
Logically this terminology should be applied without any restriction to all 
deposits, whatever their nature. T. Högbom, in his paper “ Ancient inland 
