386 Part IV. Chapter 2. 
Carex trisperma Dewey. Carex exilis Dewey. 
Dulichium spathaceum Pers. (= D. »  folliculata L. 
arundinaceum L.). » _ fusca Man. ed. 6. 
Eleocharis pauciflorus Link. »  Jlivida Willd. 
Eriophorum alpinum L. »  magellanica Man. ed. 6. 
gracile Koch. »  oligosperma Michx. 
» vaginatum L. »  pauciflora Lightf. 
Scirpus atrocinctus Fernald. »  saltuensis Bailey. 
Carex chordorrhiza L. f. »  tenella Schkuhr. 
The same Ericaceae are noted from Massachusetts bogs, without Rh. Rho- 
dora, the same Sarracenia, Geum, and the following trees, shrubs and perennials: 
Picea nigra Link. Aster junceus Ait. 
Salix candida Fluegge. Senecio Robbinsii Oakes. 
» myrtilloides Man. ed. 6 (= S. | Solidago uliginosa Nutt. 
pedicillaris Pursh). Pyrola secunda L. var. pumila Gray. 
Viburnum cassinoides L. > uliginosa Torr. 
Myrica gale L. Amelanchier canadensis T. & G. var. 
Potentilla palustris Scop. oblongifolia Roem. 
Lonicera caerulea L. Solidago neglecta T. & G. 
> oblongifolia Goldie. Valeriana sylvatica Banks (= V. sep- 
Rhamnus alnifolia L’Her. tentrionalis Rydb.). 
In many places the forests to be considered later encroache on the bogs converting them 
into boggy woodlands. In a study of certain salt marshes on the New England coast PENHALLOW 
finds that sphagnum bogs have been invaded by Alerts trifoliata, Cassandra calyculata, 
_. macrocarpon, Cyperaceae and other plants until in the lapse of time the surface of 
e bog in a condition to support the white pine, Pinus strobus. Then through the destruction 
jr the sea u salt water suddenly covered the converted bog which was changed into a salt 
marsh. The history of such salt marshes are shown by excavation and Penhallow from a study 
of the marsh layers believes that it has taken approximately 420 years for these changes to take 
place while the previous sphagnum growth was indefinite. 
Swamp Formation. This formation is coincident with open swamps and 
marshes. The water is shallow, the soil is covered with water, but in summer 
the water dries up leaving the soil of such swamps partially dry. The plants 
of this formation are entirely different from those that form the bog associations. 
They appeared in the region at a later period than the bog plants, as we 
have shown in a former chapter. The following plants are usually amphibious, 
or emersed: 
Pontederia cordata L. Acorus Calamus L. 
Alisma Plantago-aquatica L. Peltandra virginica L. (= P. undulata 
Sagittaria variabilis Engelm. (= S. lati- Raf.). 
folia Willd.). Sparganium eurycarpum Engelm. 
>» _ heterophylla Pursh (= S. > simplex Huds. 
rigida Pursh). Typha latifolia L. 
