PAPERS ON BOTANY 161 
area in question is a thick-bedded and very much weathered 
and eroded Platteville-Galena limestone, having many chert 
seams from which year in and out there continually oozes a 
lime-saturated cold clear water, giving the whole face of the 
Primrose section a very wet condition. In fact the conditions 
are largely the same as would prevail in a well drained swamp, 
Of disintegrating rock there is abundant supply, but of humus 
and ordinary soil there is practically none, and it is an interest- 
ing problem as to where the primula and other associated 
species obtain the nitrogen necessary for protoplasmic needs, 
The seeds that do germinate almost of necessity are caught by 
some portion of the rosette or lodge on the decomposing rock 
or in the numerous weathered cavities. 
The constant water seepage, beside furnishing abundant 
moisture and certain mineral elements, has marked ameliorat- 
ing effect on the rock temperature, both summer and winter. 
In summer the roots of the plant are kept constantly cool, even 
in the face of the hot afternoon sun, for all these primrose 
cliffs have a westerly exposure. In winter, on the contrary, 
the water keeps the immediate surface and surface rock layers 
above the freezing point, finally forming ice cascades that cover 
most of the cliff face, and these must effectually protect from 
the cold western blasts the delicate roots and crowns buried 
beneath them. 
This primula, as a rule, grows in a nearly pure association, 
very few if any other species intermingling. Here and there, 
however, there are little islands in the midst of, or peninsula 
like tongues extending into the primrose growth from the mar- 
gins. These are overgrown with various species of mosses, 
one or two liverworts, a Parnassia, Sullivantia, Potentilla 
fruticosa, Hypericum Canadense, Epilobium lineare, Steiro- 
nema quadriflorum, Lycopus Americanus, Mimulus ringens, 
Pedicularis lanceolata, Galium boreale, Campanula uliginosa, 
Lobelia Kalmii and Senecio obovatus. It is to be especially 
noted (as set forth in Cliff Flora of Jo Daviess Co.) that the 
above list is of typical swamp or marsh species, but which all 
through this particular region elect largely to grow on wet 
cliffs and with even greater luxuriance than when inhabiting 
the ordinary level swamp. 
