150 BOTANICAL GAZETTE [MARCH 
Larix and Thuya swamps reach but an imperfect development 
in our region and little need be said about them. The shade 
in these forest swamps is so dense that bare patches of soil are 
often seen. The vegetation consists largely of shade plants, 
among which may be mentioned Mnium and other similar mosses, 
Coptis trifolia, Cornus Canadensis, Viola blanda, and Impatiens. The 
tamaracks appear to be succeeded by the pines (Pinus Strobus or 
P. Bankstana), and they in turn by oaks, as the soil becomes 
drier and better drained, and thus more adapted to deciduous 
trees. /ig. 20 shows a tamarack swamp near Miller, Ind. 
Not all peat bogs have a history like the above. Just as 
some flood plains are forested and others not, so some peat 
bogs grow up to shrubs and trees, while others are dominated, 
for a long time at least, by herbs and grasses. Fig. 27 shows a 
swamp of this character. Bulrushes are seen to be encroach- 
ing upon the water lily vegetation, while back of the bulrushes, 
instead of Cassandra, is a zone with sedges and grasses and 
scattered willows. Among the species, other than sedges and 
grasses in a plant society like this are Viola sagittata and V. lan- 
ceolata, Potentilla Anserina, Fragaria Virginiana, Parnassia Caro- 
lintana, Sabbatia angularis, Gentiana crinita, Gerardia purpurea, 
Castilleta coccinea, Aletris farinosa, Iris versicolor, Sisyrinchium 
angustifolium, Hypoxys erecta, Xyris flexuosa, Triglochin maritima. 
The shrubs in such places are chiefly Sadix glaucophylla, Cornus 
stolonifera, Potentilla fruticosa, Hypericum Kalmianum. The con- 
ditions that determine this type of bog, as contrasted with the 
Cassandra type, are not clear. The soil is hard, compact, 
shallow, and usually sandy ; it may be that this type develops in 
shallow depressions, while the type with spongy, quaking ground 
develops in deeper depressions. This second type much more 
closely resembles the half-drained swamps in its flora than does 
the Cassandra type, although so far as drainage is concerned it 
agrees with the Cassandra bogs. 
There is yet a third type of swamp which still more closely 
resembles the half-drained swamp in its flora. It is found along 
the edge of the Calumet valley near Dune park, also at West 
