984 MINNESOTA BOTANICAL STUDIES. 



ter are the more abundant. Yet dwarfed P. deltoidea shrubs 

 are characteristic of much of the back strand along the southern 

 shore of the Grand Traverse. It is not often inundated. 



V. Salix shrubby back strand. This type characterizes 

 low, commonly inundated, rather strongly nitrogenous back 

 strand, and is found in conjunction with Salix mid- strand. It 

 does not indicate strong wind-currents and is commoner in 

 sheltered bays or behind islands than upon the shores that face 

 wide expanses of water. Various species of Salix are repre- 

 sented of which doubtless Salix lucida and Salix discolor are the 

 most abundant. 



VI. Rosaceous shrubby back strand. For miles on the Grand 

 Traverse shore this type of back strand is abundantly developed. 

 The characteristic plants are Rosa olanda and Rosa luoodsii with 

 Cerasus pennsylvanica, Gerasus virginiana and Amelanchier cana- 

 densis. In no case do the plants attain a considerable size and 

 often a shrubby formation no higher than one's head is main- 

 tained for hundreds of yards. The favorable conditions for 

 this type seem to be high banks, exposure to strong winds, ab- 

 sence of occasional inundations and a fairly high percentage of 

 nitrogenous substances in the soil. Yet sometimes a rosace- 

 ous formation is found growing upon what appears to be al- 

 most pure sand, and similar formations are found upon the 

 dunes. In general the establishment is more characteristic of 

 slopes than of summits or hollows and indicates a sensitive- 

 ness to drainage conditions and the movement of soil waters. 

 At the season of blooming for the genus Rosa, such a back 

 strand makes a bank of pink color behind the yellow Elymus 

 and Artemisia dotted mid- strand that is noticeable from the 

 decks of steamers far from shore. 



VII. Mixed shrubby back strand. This type is in point of 

 fact probably separable into minor varieties such as Vitis back 

 strand, Rhus back strand and others, but nowhere on Lake of 

 the Woods were characteristic groups developed strongly 

 enough, except from the shrubs before mentioned, to justify 

 such a nomenclature. The mixed shrubby back strand indi- 

 cates either light or fertile soil, strong wind currents and an 

 irregularity of surface contour with corresponding differences 

 in percentage of soil water between adjacent very limited areas. 

 In such a mixed shrubby back strand Quereuss crub and Frax- 

 inus with small, dwarfed individuals of Ulmus are not uncom- 

 mon. The complexity in number of species is directly con- 

 nected with the surface contour. 



