15ti Bulletin Wisconsin Natural History Society. [Vol. 8, No. 3. 



with 8.9 and 17-inch breast-high diameters, which are considerable 

 dimensions for this region. Arbor vitae forty feet high and 9 

 inches in diameter breast-high occur. No large white pines are 

 left, but near Fox Point there are vigorous saplings, up to 3 inch 

 breast-high diameters. Red cedars (which, however, are southern 

 rather than boreal trees) are quite numerous and vigorous in the 

 southern part of the area, though absent northward. 



As one walks up the ravines, it is evident that these boreal 

 elements rapidly diminish, until one finds a typical maple-beech- 

 basswood society in the upper reaches of the longer ravines, with 

 hemi-xerophytic elements prevailing on the slopes, especiallv the 

 north sides. It is apparent, therefore, that conditions are favor- 

 able for the northern xerophytes only so far as the immediate lake 

 influence goes ; farther inland they succumb to the broad-leaved 

 forest. 



The question arises: Are these boreal species invaders which 

 settled among the mesophytes of the shore and on account of Lake 

 influences are able to hold their own ; or are they relicts from a 

 former period, when boreal xerophytic forests predominated in 

 the Milwaukee region? All these species occur in numerous places 

 along the lake, to the south as well as the north. These stations are 

 not infrequently separated by considerable spaces, where they are 

 wholly absent under conditions which exclude human agency. 

 Colonization is not impossible, but it is made difficult by the fact 

 that the seeds would most likely have had to come from across the 

 lake, which is not quite credible. In the case of the junipers, birds 

 might carry them from the shore side. But winds carrying the 

 pine and birch seeds would necessarily have to be lake winds. This 

 is quite inconceivable. Ice rafts might possibly do the work, the 

 wind blowing the seeds up the bank, after they had been landed on 

 the beach. It is a fact that ice rafts bearing tree seeds can be ob- 

 served every winter. 



But these methods are so precarious that the other alternative 

 seems decidedly more plausible. In the distant past, the Milwau- 

 kee region was covered with pine forests similar to those now oc- 

 curring farther north. Changes, perhaps of a climatic nature, 

 caused these to succumb to broad-leaved species ; and now the 



9) However, as stated above, paper birch occurs commonly anywhere 

 east of the Milwaukee River; and at the time of the settlement white pine is 

 said to have been common in the same territory — a mile or more from the 

 Lake. 



