212 BOTANICAL GAZETTE [MARCH 
involving somewhat different courses of succession. One had an 
abundant growth of sphagnum associated with much Ledum, and 
Picea mariana and Larix composing the bog forest. Those of the 
other type had little sphagnum, often practically none, and in 
these Ledum was rare or absent and Picea mariana almost never 
found, the bog trees being Larix and Thuja or Larix alone. The 
Raspberry Island bog is an excellent example of the first, which we 
may designate the sphagnum type; and Sucker Lake and the 
other pond near Tobin’s Harbor illustrate the second, or sedge 
type. In some cases these types may represent stages in the same 
succession, since sphagnum often does not become dominant until 
late in the history of a bog, and Ledum and Picea mariana follow 
the sphagnum, being dependent upon its presence. But it is 
certain that in many cases the Sphagnum-Ledum stage is entirely 
eliminated, and that when this happens Picea mariana does not 
appear, or holds a very subordinate place in the bog forest. The 
succession in such cases is as follows: (1) aquatics, (2) sedge mat, 
(3) shrub zone (Chamaedaphne, Andromeda, Alnus incana), (4) bog 
forest (Larix, often with Thuja). It is obvious that Sphagnum is 
the critical plant, since Leduwm and Picea mariana come later and 
only in bogs where the moss is abundant. 
Certain differences were noted in the conditions prevailing in 
the two types of bogs. It was universally true in the sphagnum 
bogs that were visited that the drainage was poor or lacking, the 
only water loss being due to very slow seepage and evaporation. 
Those of the sedge type on the contrary were usually well drained. 
There was often open water in the center, in which case the bog 
might well be at a stage earlier than that of sphagnum dominance. 
The covered bogs without much sphagnum usually possessed one 
or more small streams flowing in and an active outlet. In a few 
cases, however, the drainage was seemingly as poor as in the 
sphagnum bogs. As to the way in which these drainage differences 
affect the vegetation, if they do affect it, nothing was determined. 
Another fact was noted which quite certainly has a bearing upon 
the presence or absence of sphagnum. It was found that the sedge 
mat is composed of different species in the two types of bogs. In 
the sphagnum bogs Carex limosa, a low, soft, loosely growing 
