Hydrophyllum appendiculatum. 
Hydrophyllum virginianum. 
Arisema diphylla. 
Trillium grandiflorum. 
Trillium cernuum. . 
*Trientalis americana. 
*Maianthomum canadense. 
Senecio aureus. 
Botryehium virginianum. 
Osmunda regalis. 
Osmunda cinnamomea. 
Pteris aquilina. 
Cystopteris fragilis. 
Aspidium spinulosum. 
Aspidium eristatum. 
Aspidium thelypteris. 
Adiantum pedatum. 
Anoclea sensibilis. 
Camptosorus rhizophylius. 
Asplenium aecrosticoides. 
*Lycopodium lucidulum. 
On the west side of the arbor vitae association is an almost undisturbed 
tree association, differing greatly in composition from that just described. 
The arbor vitae zone is made up largely of plants of northern origin or plants 
characteristic of bogs, while the plants of the other group, called the maple- 
tulip association, are those typical of the climax mesophytie forest of the 
region and are distinctly southern in their origin. A comparison of the 
distribution of the more distinctly boreal forms of the arbor vitae associa- 
tiln, indicated thus (*) in the list, with those given below for the maple- 
tulip association, will make the difference in origin very striking. Practically 
all these boreal forms occur outside the limits of distribution given by the 
best manuals. The beech is usually a member of the climax mesophytie 
forest of this region, but since for some reason it is absent from all the forests 
of this vicinity for several miles around, it is also absent in the bog. The 
principal trees of the maple-tulip association follow: 
