1911] Fernald,— Expedition to Newfoundland 161 
dences which demand, since the Glacial Period, a decided subsidence 
outside that line. 
If we now examine the lists of characteristic plants of Class III, the 
Southwestern plants which, it seems to me, must have crossed from: 
southern New England to Newfoundland on this bridge, we shall see 
that they are all species typical of our more purely silicious plains, 
sterile hills, or acid bogs, but not of the better mixed soils such as the 
glacial till; many of them being plants which in New Jersey are today 
abundant only on the Cretaceous and Tertiary clays, sands and gravels 
and which farther south are almost confined to the Coastal Plain and 
similar areas.! If, on the other hand, we examine the list of char- 
acteristic Canadian plants which, though abundant on the west side 
of the Gulf of St. Lawrence, are unknown in Newfoundland, we shall 
see that they are chiefly species of rich woods, meadows or other well 
mixed soils, or highly calcareous ledges and gravels. 
When, therefore, we consider the fact that the bridge formed by the 
elevated coastal plain was composed of silicious soils presumably 
identical with those found upon the southern Coastal Plain of ouf 
present continent it is evident that an ideal route was laid out for the 
spread northeastward of the plants which prosper chiefly in such soils 
and it is easy to picture the Red Pine, Pinus resinosa, accompanied or 
soon followed by Schizaea pusilla, Corema Conradii, Hudsonia ericoides, 
and the other southwestern plants of highly silicious regions, pushing 
successfully across the bridge to Newfoundland, while Sabatia do- 
decandra got as far as Sable Island and Ilex glabra reached the sandy 
swamps of Nova Scotia. Here too, in the boggy meadows and about 
the shallow pools, would be a habitat over which the vole and the 
musk-rat would rapidly spread. But such a very silicious region would 
have been highly unattractive to Adiantum pedatum, Thuja occidentalis, 
Carex retrorsa, Lilium canadense, Calypso bulbosa, Anemone riparia, 
Dalibarda repens, Lonicera canadensis, Viburnum alnifolium, Solidago 
squarrosa, Aster macrophyllus, and the hundreds of other plants of 
richer soils, which not only in eastern Canada but farther south 
(when they occur there) scrupulously avoid the more sterile areas; 
and even if they did occasionally straggle slightly off the richer soils 
1 Compare, for example, Britton, Bull. Torr. Bot. Cl. vii. 81 (1880) and Cat. Pl. 
N. J. (1889); Hollick, Trans. N. Y. Acad. Sci. xii. 191, etc. (1893) and Am. Nat. xxxiii. 
1-14, 109-116 (1899); R. M. Harper, Ruopora, vii. 69 (1905), viii. 27 (1906). 
