state convention—Geological survey. 323 
ness of such a map in studying the adaptabilities of these areas 
and in drawing correct conclusions from the experience of others.] 
The significance of the native vegetation is illustrated more de¬ 
cidedly perhaps in some of the marsh vegetation, than elsewhere. 
A marsh covered with certain classes of plants is very readily im¬ 
proved, but only with difficulty if covered with certain other 
kinds. Certain plants indicate a suitable bottom for the culture 
of cranberries, certain others that the conditions arc altogether 
unfavorable. The natural distribution of this plant, the cran¬ 
berry, may be taken as a well marked illustration of what is taught 
in a greater or less degree by every plant, and will indicate what 
I desire to enforce in this connection better than any abstract 
statement, and it has the further advantage of being a subject 
concerning which interest is just now awakened. 
It should first be stated that the elements required for the suc¬ 
cessful culture of the cranberry seem to be the following, briefly 
stated : First, a suitable bottom, a good bed of peat is the best,, 
that being the principal food of the plant. At the East, cedar 
swamp bottoms are preferred. Our tamarack swamps would doubt¬ 
less prove equally satisfactory. Secondly, complete control of the 
drainage, so that the marsh may be drained or flooded as may be 
demanded. Thirdly, a sufficient supply of silica. “ Silica 
plants ” differ from “ peat plants ” in the appearance, mode of 
growth, and in a much superior yield. 
Keeping this last requirement in mind, let us examine their na¬ 
tive distribution. The chief marshes that lie within the district 
inspected by me during the past summer readily arrange them¬ 
selves in three groups and show an interesting relationship to the 
geological formation. Those at the north form one group and 
rest upon the Potsdam sandstone. Those in Oconomowoc, Dela- 
field, Concord, Summit, Ottawa, Eagle, Richmond and Sugar 
Creek, form a numerous group of small marshes lying in the san¬ 
dy district, that seem to have had its origin in the arenaceous lay¬ 
ers of the shode. The third group comprises those in the western 
part of Jefferson county which lie upon or near the St. Peters 
sandstone. The demand for silica is thus shown in the natural 
distribution of the plant. But more is indicated. Their growth 
is limited to certain latitudes, or more strictly, to certain climatic 
