62 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



10. TYPHACEAE. Cat-tail Family. 



1. TYPHA L. Cat-tail. 



Staminate and pistillate portions of the spike distant; leaves 5 mm, wide. 



1. T. angustifolia. 

 Staminate and pistillate portions of tho spike contiguous; leaves 10 mm, wide. 



2. T. latiiolia. 



1. T3rpha angustifolia L. 



Marshes and wet places, forming colonies. Eur., Asia, and N. Amer. north of Mex. 



2. Typha latifolia L. 



Marshes and wet places, forming colonies. Eur., Asia, and N. Amer. 



11. SPARGANIACEAE. Bur-reed Family. 



1. SPARGANIUM L. Bur-reed. 



Fertile flowers sessile; fruit broadly obovoid 1. S. eurycarpum. 



Fertile flowers short-pediceled; fi-uit fusiform. 



Inflorescence simple 2. S. americanum. 



Inflorescence with 1 or 2 weak branches from lower axils. 



2a. S. americanum androcladum. 



1. Sparganium eurycarpum Engelm. 



Frequent in swamps and marshy margins of streams. Fr. July-Aug. Widely dis- 

 tributed in N. Amer. 



2. Sparganium americanum Nutt. 



Frequent in the same situations as the last, but usually in shallower water. June- 

 July; fr. Sept. Eastern N. Amer. and Asia. 

 2a. Spatganium americanum androcladum (Engelm.) Fern. & Fames. 



Habitat and range same as for the species. {S. androcladum jMorong; S. simplex 

 androcladum Engelm.) 



12. POTAMOGETONACEAE. Pondweed Family. 



Leaves alternate; fruit subglobose, short-beaked; flowers perfect. 



1. POTAMOGETON. 



Leaves opposite; fruit oblong, long-beaked; flowers monoecious. 



2. zannichellia: 



1. POTAMOGETON L. Pondweed. 



Leaves of two sorts, the thicker floating ones with a dilated petio^ed l^lade, different 

 in form from the thinner submersed ones. 



Submersed leaves less than 2 mm. wide 10. P. diver sifolius . 



Submersed leaves more than 2 mm. wide. 



Submersed leaves linear, with a broad, coarsely cellular-reticulate space each 



side of the midrib 1 • P • epihydrus . 



Sul^mersed leaves broader than linear, not differentially reticulate. 

 Floating leaves 30-50- veined ; submersed leaves large, wide, often much 



recurved 3. P. amplifolius . 



Floating leaves fewer- veined ; submersed leaves narrowly lanceolate. 



2. P. americanus. 



