EARLY INVESTIGATIONS. 15 



at a later period and under much less favorable conditions than those of 

 the forests preserved in layer r. 



An oak period must have followed that in which these stunted pines grew, 

 as oak trunks occur directly above layer q. Oak leaves and fruits were rare 

 about the trunks, but on the marginal slopes remains of the oak {Quercus 

 sessiliflora) dominate the layer s. They become recognizable only with diffi- 

 culty in the upper part of the layer, which then passes gradually into an alder 

 layer t. The latter is the top layer of the moor, covering the oak one to a 

 depth of 3 to 4 feet, both at the margin and in the center. Oaks occur occa- 

 sionally in this layer, though the alders are wholly predominant, their branches, 

 leaves, and catkins sometimes forming the peat alone. The large number 

 of nuts indicates that hazel (Coryliis avellana) probably formed a considerable 

 portion of this layer, especially near the margins. In the nothern portion of 

 the moor the Hypnum layer contained leaves of Eriophorum angustifoUum, 

 and scattered trunks of Betvla. 





Fig. 2. — Section of Lillemose moor, showing central and marginal layers of the 

 cosere. After Steenstrup. 



In the Lillemose Moor, the structure is indicated by the cross-section shown 

 in figure 2, in which the following layers are seen, from below upward: 



Central Area. Margins. 



('. Sphagnum with alder t. Alder. 



u. Hypnum proUferum with remains of birch and oak. 



q. Sphagnum with oak, above with Oxycoccus, Eriophorum, etc s. Oak. 



p. Hypnum cordifolium with pine and some aspen r. Pine. 



n. Silica layer with Potamogeton and aspen c. Drift. 



d. Sandy clay, the substratum d. Sandy clay. 



The lower part of layer n seems almost a continuation of d, but the upper 

 portion clearly shows the remains of Hypnum cordifolium. Potamogeton, 

 Equisetum, Myriophyllum, Alisma, and especially leaves and twigs of Populus 

 tremvla everywhere in the layer, showing that the latter grew upon the mar- 

 ginal slopes. This foliated silica layer is covered by a peat layer of Hypnum, p, 

 which is also in direct contact with the substratum over some parts of the 

 banks. Pine needles and cones occur with the IJypnum, and on the margin 

 become so abundant as to form a layer r, which consists almost wholly of pine 

 cones, needles, and bark, mixed with some Hypnum fluitans. The pine layer 

 also contains remains of Betvla, Salix, and Menyanthes. Above the pine 

 stratum lies the oak layer, containing twigs, leaves, acorns, cups, and an occa- 

 sional trunk of Quereus sessiliflora. The next layer is that of alder peat, com- 

 posed almost whoUy of Alnv^ glvtinosa, but with an occasional Betvla or Salix. 

 This uppermost layer covers the entire surface of the moor as well as the 

 margins. In the center of the moor, the layer n is covered by Hypnum peat, p, 

 which is pure below, except for roots of Nymphaea, leaves of Populus and ScAix, 



