38 THE PLANT SOCIETIES OF 



to deciduous trees. Fig. 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. 



Fig. 21. — Shallow, undrained swamp (peat bog) at Dune Park. In the foreground the 

 relict of the original pond, with water lilies, then in order, encroaching zones of bulrushes- 

 sedges, willows, and pines. The oaks in the b^kground are on an established dune, and are 

 not encroaching on the swampy soil. 



by herbs and grasses. Fig. 21 shows a swamp of this character. Bul- 

 rushes are seen to be encroaching 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 (Strawberry), Par- 

 nassia Caroliniana, Sabbatia angularis, Gentiana crinita, Gerardia pur- 

 iurea, Castilleia coccinea (Painted cup), Aletris farinosa. Iris versicolor, 



