MICHIGAN ACADEMY OF SCIENCE. 127 



ON THE DISTRIBUTION OF ACER SPICATUM LAM., AND ACER 

 PENNSYLVANICUM L. IN THE NORTHERN PENIN- 

 SULA OF MICHIGAN. 



Charles A. Davis. 



In rather extensive travels over considerable areas of the Northern Pe- 

 ninsula during two field seasons, the writer has been impressed with the 

 marked differences exhibited in the range and the variations of habitat of 

 the two shrubby species of maple, Acer Pennsylvanicum L., the Striped 

 Maple, and Acer spicatum Lam., the Mountain Maple. In the Michigan 

 Flora, 1904, the distribution of Acer Pennsylvanicum is given as "abundant 

 in the Northern Peninsula, Whitney. Common at Petoskey and occasional 

 as far south on the Huron shore as Alcona Co., Winchell Catalogue; in the 

 interior as far as Houghton Lake. N. and U. P." 



That of Acer spicatum is given as "Common in the Northern Peninsula; 

 Alcona Co.. Winchell's Catalogue; Crystal Lake, Montcalm Co., Alma; C, 

 N, and U. P." From these notes one would infer that the two species had 

 about the same distribution in the Northern Peninsula, and that they were 

 equally abundant throughout those parts of their ranges in which they oc- 

 cur together. Such is not the case, however, according to the experience 

 of the writer. It is true that Acer spicatum is widely distributed and fre- 

 ciuently a very abundant plant in two types of habitat, over most of the 

 Northern Peninsula; it occurs in the dryer parts of swamps and in greater 

 quantity in their borders, and as one proceeds northwards, becomes one of 

 the more important constituents of the undergrowth in the mesophytic 

 forest, often forming dense thickets in and around clearings and at the sides 

 of wood-roads and other artificial and natural openings in the forest. In 

 such places it often is so thick and shades the ground so heavily that it must 

 tend to check, to a considerable extent, the natural reproduction of all but 

 the most tolerant of the dominant forest trees. 



The plant in its best development is scarcely more than a tall shrub, L5 

 to 25 feet high, very tolerant of shade, but flourishing in the better light of 

 the openings, and is worthless for any purpose, the wood being exceedingly 

 brittle and soft, and the diameter rarely as much as three inches. This 

 species is common throughout the region under discussion, wherever the 

 hardwood timber grows, and is not infrequent in the moister parts of the 

 types of soil formerly covered by the pines. It is often abundant in rocky 

 hardwood forests, and upon open talus-slopes, against the bases of steep 

 cliffs, but rarely appears as a crevice plant on the exposed cliffs. It is rarely 

 or never an inhabitant of the wet areas of swamps, but, as noted above, 

 habitually occurs about their borders, especially towards the southern part 

 of the peninsula. 



Acer Pennsylvanicum, on the other hand, has a very much more restricted 

 range, both laterally, in that it does not occur so generally, and vertically, 

 because it has much less varied habitat. In the summer of 1905, when at- 

 tached to the party of Professor I. C. Russell, working in the interior of 

 Menominee county, and in Dickinson and Iron counties, this species was 



