Rosendahl: observations on betula 453 



It is not necessary here to describe the first three species, for 

 they are quite common throughout their range, easily recognized 

 and generally well known. Some facts about their distribution in 

 the middle northwest are worth noting. 



Betula lenta L. is reported to range as far west as northern 

 Ontario and central Iowa. From this one would expect it to occur 

 within the borders of Minnesota, and in fact several specimens 

 labelled B. lenta have been collected in different parts of the state. 

 None of these proves upon careful examination to be correctly de- 

 termined. One of these, by W. A. Wheeler (No. 1651) from south- 

 eastern Houston County, has leaves which in outline resemble very 

 closely typical B. lenta leaves, but the serrations are too coarse and 

 uneven, and the bracts are conspicuously ciliate-pubescent along the 

 margins. The specimen can therefore be referred to B. Intea with- 

 out any doubt whatever. There is nothing in the present topog- 

 raphy nor anything of the nature of geologic barriers to prevent 

 B. lenta from occurring in Minnesota if the report of its two western 

 outposts given in standard manuals and floras is correct. We are 

 therefore constrained to regard its occurrence in northwestern 

 Ontario as doubtful. 



Betula lutea Michx. occurs as a tree of varying height, reaching 

 its greatest size on the wooded slopes and side gullies of the St. 

 Croix and Mississippi River valleys, where it usually grows to a 

 height of 50 to 70 feet and a trunk diameter of 12 to 18 inches. It 

 is found short distances up some of the valleys of the western 

 tributaries of the Mississippi from the southern border of the state 

 to the Minnesota River, and is also common in the tamarack swamps 

 of the east central and northeastern parts of the state. In these 

 localities it is smaller and is more irregular and spreading. 



A few puzzling forms of this species occur, some with the fruit- 

 ing catkins much reduced in size, others with thick, leathery leaves. 

 Possibly these are other hybrids or Mendelian segregates. At pres- 

 ent material is insufficient and not enough observations have been 

 made in the field to warrant any disposition of them. 



Betula papyrifera Marsh, is common throughout "the wooded 

 areas of the state and is quite variable in general appearance as 

 well as in foliage and fruit. 



On the north shore of Lake Superior B. papyrifera var. cordi- 

 folia Regel. is common and attains great size. In fact, some of the 



