242 
flowers alternate. Staminate petals four, longer than the stamens, 
oblong, pale, rose-colored, deciduous. Stamens eight. Fruit 
looking like a square block, 14% mm. long and broad. Carpels 
turgid, rounded on the back with a deep intervening groove. A 
deep water plant. 
Greenland, Lake Termiscouata (Northrop), and Lake Mem- 
phremagog, Canada, near the United States boundary (Churchill). 
Common in Europe. 
3. MM. verticillatum. L. Sp. Pl. 992 (1753). 
Submerged leaves in crowded verticils of threes and fours, I to 
4 cm. long, the capillary divisions ten to twelve pairs, often min- 
utely scabrate. Floral leaves pectinate-pinnatifid, or pectinate, 
much longer than the flowers. Petals four, purplish in color on 
the sterile flowers. Stamens eight. Fruit 2 to 3 mm. long, and 
2% mm. broad, somewhat gibbous at the base. 
In deep and shallow water. Ontario (Macoun’s Cat.). Same 
range in United States as No. 2. Common in Europe. 
4. M. tenellum. Big. Fl. Bost. 346 (1824). 
Stems slender, scape-like, nearly leafless, simple, erect, 4 to 
35 cm. high, nearly all out of the water, from a long rhizome, 
which sends up many sterile shoots. Flowers alternate, solitary’ 
subtended by small, entire bracts, the uppermost obovate and often 
longer than the flowers, the lower oblong and generally shorter 
than the flowers, the lowest part of the spike often bractless. 
Stem with scattered bracts or often naked. Staminate petals four, 
longer than the stamens, somewhat persistent, purplish in color. 
Stamens four. Fruit 1 mm. long and I mm. broad at the apex, 
spreading to 1% mm. at the base. Carpels rounded or obtusely 
angled on the back, the groove shallow. 
Frequent in Canada, New England, New York, Pennsylvania, 
and west to Michigan. 
5. M. humile. (Raf). 
Purshia humilis. Raf. Med. Rep. 2nd. Hex. 3, 422 (1806). 
M. ambiguum var. \imosum., Nutt. Gen. 2, 212 (1818). Torr. 
Comp. 355 (1826). Gr. Man. Ed. 1, 140 (1848). 
This plant occurs in several forms according to the situation in 
which it grows. These forms, when seen only in dried herbari- 
um specimens, might be easily mistaken for distinct species, so 
