278 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



1. Sparganium multipedunculatum (Morong) Rydb. Occasional at low and middle 

 altitudes, about ponds. B. C. to Calif., Colo., and Ont. — Leaves 20 to 50 cm. long; 

 fruit heads 2 to 6, the lower ones stalked. 



2. Sparganium angustifolium Michx. Frequent at low and middle altitudes, in 

 lakes, ponds, or slow-flowing streams. B. C. to Calif., N. Mex., Pa., and Newf. — 

 Plants slender, the leaves usually floating, 30 to 60 cm. long; fruit heads 2 to 4, 

 sessile or the lowest one stalked. 



10. POTAMOGETONACEAE. Pondweed Family. 



Aquatic perennials with slender, usually branched stems; leaves broad or narrow; 

 flowers very small, green, in axillary clusters or spikes; petals and sepals none; fruit 

 a small achene or drupelet. 



Leaves opposite; flowers sessile in the leaf axils; fruit with a long slender beak. 



1. ZANNICHELLIA. 

 Leaves alternate; flowers in spikes; fruit with a very short beak. 



2. POTAMOGETON. 

 1. ZANNICHELLIA L. 



1. Zaunichellia palustris L. Horned pondweed. Collected in pools at east 

 entrance by Umbach. Widely distributed in N. Amer. and the Old World. — Stems 

 very slender, submerged; leaves threadlike, 3 to 6 cm. long, 0.5 mm. wide or less, 

 1-nerv^ed; fruit 2 to 6 mm. long. 



2. POTAMOGETON L. Pondweed. 



Leaves often of two kinds, some floating and some submerged, with stipules. — It 

 is probable that several other species besides those listed below occur in the park, 

 for the writer was unable to make very extensive collections. The water in many 

 of the lakes appears to be too cold for the growth of the plants, but they are plentiful 

 in Lake McDonald and St. Mary Lake. 

 Plants with both floating and submerged leaves. 



Floating leaves mostly 1.5 to 4 cm. long 1. P. heterophylltis. 



Floating leaves mostly 5 to 12 cm. long. 



Submerged leaves without blades 2. P. natans. 



Submerged leaves with large blades 3. P. amplifolius. 



Plants -nith submerged leaves only. 



Leaves lanceolate or linear-lanceolate, many-nerved, 8 to 30 mm. wide. 



Leaves sessile or short-petioled, not clasping 4. P. lucens. 



Leaves clasping 5. P. richardsonii. 



Leaves linear or threadlike, few-nerved, 3 mm. wide or less. 

 Stipules free from the petioles and blades. 



Leaves with 2 glands at the base, 1 to 1.5 mm. wide 6. P. pusillus. 



Leaves without glands, 2 to 4 mm. wide 7. P. compressus. 



Stipules united with the bases of the leaves. 



Leaves linear, about 1 mm. wide 8. P. interior. 



Leaves threadlike, 0.5 mm. wide or less 9. P. pectinatus. 



1. Potamogeton heterophyllus Schreb. Fish Lake. B. C. to Calif., Fla., and Lab.; 

 also in Eur. — Floating leaves oval, green, 9 to 19-nerved; submerged leaves linear or 

 linear-lanceolate, 2 to 12 mm. wide. 



2. Potamogeton natans L. Small pond along trail to Avalanche Lake. Widely 

 distributed in N. Amer., Eur., and Asia. — Floating leaves oval or ovate, 5 to 10 cm. 

 long, rounded at the apex, usually subcordate at base, thick, 21 to 29-nerved. 



3. Potamogeton amplifolius Tuckerm. Fish Lake. B. C. to N. B. and Ga. — 

 Floating leaves oval or ovate, usually acute, rounded or subcordate at base, 6 to 15 

 cm. long; submerged leaves lanceolate or elliptic, ruffled, thin. 



