BEAL ON MICHIGAN FLORA. 13 



mazoo and St. Joseph counties. The Saginaw bay branch of the Huron 

 glacier unites with tlie Huron glacier proper, and forms a lateral moraine 

 beginning in Huron county, passing through Sanilac, Lapeer, Oakland. 

 Livingston and portions of Jackson, Washtenaw and Hillsdale counties. 

 This peninsula is divided by these moraines into certain more or less 

 clearly marked floral regions, 



CLIMATE AND DISTRIBUTION. 



"The sinuosities of the several isothermal lines will demonstrate at a 

 glance the peculiar character of the climate of Michigan, and the fact that 

 both in summer and winter, it is better adapted to the interests of agri- 

 culture and horticulture, and probably also to the comfort and health of 

 its citizens, than the climate of any other northwestern state. The marked 

 peculiarity of the climate of Michigan in these respects is attributable to 

 the influence of the great lakes by which the state is nearly surrounded. 

 It has long been known that considerable bodies of water exert a local 

 influence in modifying climate and especially in averting frosts, but it has 

 never been expected that Lake Michigan, for instance, impresses upon the 

 climatic character of a broad region an influence truly comparable with 

 that exerted by the great ocean." — Alexander Winchell. 



The following general notes on Climate and Distribution are from the 

 preface to the first edition by E. F. Smith : 



•'The influence of climate on vegetation may be summed up in a few 

 words. The climate of the Lower Peninsula is not as severe as that of the 

 Upper, nor so even, but is subject to frequent, sudden, and extreme 

 changes of temperature — as great a variation during the winter season 

 as 53° Fahr. in less than 24 hours having been recorded. Such rapid 

 changes more or less attect vegetation, especially the tender branches of 

 cultivated trees, which are sometimes seriously injured. In one or two 

 instances a like effect on our forest trees has been noticed. The annual 

 range of temperature is about 116°, and the annual mean 46°. Of rain- 

 fall, including what falls in form of snow, we have, yearly, about thirty 

 inches. Our snowfall is much less, for the same latitude, than that of 

 New York and New England. In the center of the peninsula, we seldom 

 have more than a few inches at a time. 



"The proximity of the Great Lakes exerts a marked influence in equal- 

 izing the temperature and the effects are marked upon our flora. 



"Trees, like Liriodendron Tulipifera, Asimina triloba, Ccrcis Canaden- 

 sis, Gleditsia triacantlws , Cornus florida, Nyssa multiflora, and Morus 

 rubra, which belong to Ohio and Central Illinois, have crept northward, 

 favored by the mild influence of the lake winds, through the central and 

 western part of the Lower Peninsula, often beyond the middle, and the 

 same is true of smaller and less noticeable plants. 



"As might be expected from the uniform surface of the peninsula, the 

 flora is much alike throughout. Probably three- fourths of our species are 

 common to all sections, though by no means equally distributed; some 

 being very abundant in one district and rare in another at no great dis- 

 tance. In most cases such change is due to soil rather than to difference 

 in elevation, temperature, or atmospheric moisture. 



"The Lower Peninsula is covered with a deep drift of alternating sands, 

 clays, and gTavels, and the flora of any section depends chiefly on which 

 of these happens to lie uppermost. With reference to its flora, the penin- 



