79 



13a. Flowers 23 cm. wide, purple (7 20 dm. high) 



Fireweed, Epilobium angustifolium. 



13b. Flowers about 1 cm. wide 14. 



14a. Flowers red (2 5 dm. high) Gaura ; Gaura coccinea. 



14b. Flowers white, turning pink when old 



Gaura, Gaura biennis. 



15a. Leaves entire, the margins usually somewhat revolute 16. 

 15b. Leaves toothed, flat (49 dm. high) 18. 



16a. Plant densely pubescent with spreading hairs (3 8 dm. 

 high) Willow Herb, Epilobium molle. 



16b. Plant pubescent with appressed or incurved hairs 17. 



17a. Leaves linear, the margin revolute (3 5 dm. high) 



Willow Herb, Epilobium densum. 



17b. Leaves narrowly lanceolate, not revolute (2 4 dm. high) 



Willow Herb, Epilobium palustre. 



18a. Seeds tipped with a tuft of reddish-brown hairs 



Willow Herb, Epilobium coloratura. 

 18b. Seeds tipped with a tuft of white hairs 



Willow Herb, Epilobium adenocaulon. 



HALORAGIDACEAE, the Water Milfoil Family 



Aquatic or marsh herbs, with alternate, opposite, or whorled 

 leaves, and small, inconspicuous terminal or axillary flowers, fre- 

 quently without petals (summer). 



la. Leaves none, or else very small and inconspicuous 



Water Milfoil, Myriophyllum tenellnm. 



Ib. Leaves alternate (1 4 dm. high) 



Mermaid Weed, Proserpinaca palustris. 



Ic. Leaves opposite or whorled 2. 



2a. Leaves entire (24 dm. high) 



Mare's-tail, Hippuris viilgaris. 



2b. Leaves toothed or dissected (Water Milfoil) 3. 



3a. Flowers in the axils of foliage leaves 4. 



3b. Flowers in terminal spikes, subtended by bracts 5. 



4a. Flowers above water, subtended by toothed or entire leaves 

 Water Milfoil, Myriophyllum heterophyllum. 

 4b. Flowers submerged, subtended by dissected leaves 



Water Milfoil, Myriophyllum farwellii. 

 5a. Flowers solitary or in pairs at each joint of the spike 



Water Milfoil, Myriophyllum alternifolium. 

 5b. Flowers several at each joint of the spike 6. 



6a. Bracts deeply pinnatifid 



Water Milfoil, Myriophyllum Terticillatum var. pectinatum. 

 6b. Bracts entire or toothed 



Water Milfoil, Myriophyllum spicatum. 



