Index to Illustrations* 



FIG. i. In the forest district. Growth of white pines and spruces upon 

 a rocky island. Steamboat channel, Lake of the Woods. 

 After photograph by the author ............................ 7 



FIG. 2. Prairie scene on the Coteau. Sunflowers line the roadway on 



either side. After photograph by Mr. R. S. Mackintosh ..... 9 



FIG. 3. Roadside vegetation. Grasses and pulses. An elm tree in 



background. Cedar lake. After photograph by Williams... 10 



FIG. 4. Spruces forming a zone around a peat-bog. Farther back are 

 tamaracks and pines. The shrub in the foreground is the 

 bog-willow, while the flowers are those of an orchid, Pogo- 

 nia. Near Grand Rapids. After photograph by Mr. Warren 

 Pendergast ................................................ 1 1 



FIG. 5. Zones of aquatic vegetation. In the center pond-lilies; at the 

 edge smartweed; farther back cat-tails, blue flags, sweet flags 

 and sedges; still farther back soft turf with grass, moss, 

 sedge and milkweed. After photograph by Williams ........ 12 



FIG. 6. Island in the Mississippi above St. Paul. The center is occu- 

 pied by elms while the rim is fringed with willows. An ex- 

 ample of a "minor tension." After photograph by Professor 

 W. R. Appleby ............................................ 14 



FIG. 7. Lake border vegetation of cat-tails, grasses, reeds and sedges. 



Lake of the Isles. After photograph by Williams ........... 18 



FIG. 8. Portion of a board which had been standing in the tank shown 

 in Fig. 10. It is encrusted with limestone deposited by a 

 colony of blue-green algae. After photograph by Miss Jos- 

 ephine E. Tilclen. From the Botanical Gazette ............... 31 



