258 DAVENPORT ACADEMY OF SCIENCES. 



Populus, Tourn. Poplar. 



767. P. alba, L. Silver Leaf. 

 Roadsides ; common. 



768. P. tremuloides, Michx. American Aspen. 

 Woods ; infrequent. 



769. P. grandidentata, Michx. Large-toothed Aspen. 

 Open woods ; frequent. 



770. P. monilifera, Ait. Cottonwood. 

 Planted extensively. 



CERATOPHYLLACE^. 



Ceratophyllum, L. 



771. C. demersum, L. Horn wort. 



Ponds and slow-flowing water; frequent. 



CONIFERS. 



Pinus, Tourn. 



772. P. Strobus, L. White Pine. 



A few large trees grow on cliffs at Wild Cat Den. 

 Juniperus, L. 



773. J. Virginiana, L. Red Cedar. 

 Rocky hillsides ; infrequent. 



HYDROCHARIDACEiE. 



Elodea, Michx. 



774. E. Canadensis, Michx. Water Weed. 

 Ponds and slow streams ; frequent. 



Vallisneria, L. 



775. V. spiralis, L. Tape Grass. Eel Grass. 

 Ponds of Mississippi River islands. 



ORCHIDACE^. 



Microstylis, Nutt. 



776. M. ophioglossoides, Nutt. Adder's Mouth. 



Woods along Millar's Creek in Bloomington Township. 

 Collected once, 1892. (Mackenzie.) 

 Liparis, Richard. Twayblade. 



777. L. liliifolia, Richard. 



Moist woods; Allen's Grove, Wild Cat Den., etc.; infrequent. 



