90 The Rum River Valley as a Botanical District. 



sisting mostly of oak and elm. In many places this has been 

 cut off and the characteristic plants of burnt wood-lands 

 have become introduced. 



South of Princeton sand dunes and oak openings prevail. 

 Here almost the only trees for miles around are Quercus 

 macrocarpa Michx. and Quercus velutina Lam. 



Heretofore there has been, to my knov^ledge, almost no 

 collecting and identification of material in this valley, which 

 seems to present comparatively so little of the effect which 

 agricultural development always has on a given area. So, 

 we find very few cosmopolitan species, and these are found 

 contiguous to the railroad and near the few and scattered 

 farm houses and claim shanties. 



Very interesting are the orchids found in the swamps and 

 damp woods. Most frequent to appear is Hahenaria broc- 

 trata R. Br. This plant, while never occurring abundantly 

 in any one place, nevertheless is found throughout the whole 

 valley wherever anything approaching the condition of hard- 

 wood swamps is found. Hahenaria tridentata Hook, and 

 Habenaria obtusata Rich, were found sparingly in a little 

 swamp near Nicholas, Aitkin county. Corallorhiza coral- 

 lorhiza (L) Karst., Cypripedium acaule Ait. and Cypripe- 

 dium arietinum R. Br. occur more frequently. Achroanthes 

 unifolia (Mx.) Raf.is another rare orchid found growing lux- 

 uriantly in a swampy opening near Yineland, Crow Wing 

 county. In all specimens examined, last mentioned species, 

 the pollinia occur singly in each cell. 



Petorites palmata (Hook) Gray was found but it is local 

 in its occurrence. It prefers low, damp situations on the 

 edges of sv^ramps and is frequently found in open groves of 

 poplar saplings. _ 



Gilia linearis (Nutt) Gray is abundant along the sandy 

 beach of Mille Lacs lake, especially on the north and west 

 shores. 



This plant is very local in its range in Minnesota. Dr. 

 Sandberg found it at Red Wing in 1885. Aside from this the 

 Mille Lacs locality is the only one that is definitely known 

 for this plant in the state. From these two eastern Minne- 

 sota localities it is reported westward to the Pacific. 



Physolis grandi£ora Hook., a distinctive plant of the 



