240. 
but with a more limited range, occurring in sandy ponds along 
the Atlantic coast from Southern New England to Florida and 
Louisiana. 
In order to compare the number of spinulose teeth in the sub- 
merged leaves of the two species, fourteen of each were taken at 
random and examined. In P. palustris thirteen plants had them 
on nearly all the leaf segments and one bore them occasionally, 
while in P. fectinata eleven were entirely destitute of them, and 
three showed them occasionally, and these so minute as to be 
scarcely discernible under a lens. 
4. Myriophyllum. L. Gen. Pl. n. 724 (1737). 
Leaves for the most part verticillate (alternate in No. 4), the 
emersed bract-like, entire, toothed or pectinate, the submerged 
long, pectinate-pinnatifid, with fine capillary divisions. Flowers 
axillary, commonly monoecious, the staminate above with a very 
short calyx tube, and two to four-lobed limb or none. Petals two 
to four. Stamens four to eight. The intermediate flowers not 
unfrequently perfect. Calyx of the fertile flowers with a more or 
less deeply four-grooved tube, and four minute lobes or none. 
Ovary two to four-celled, having a single pendulous ovule in each 
cell. Styles four, short, often plumose and recurved. Drupe 
four-sided, splitting at maturity into four crustaceous, one-seeded, 
indehiscent carpels, which are smooth, angled or tuberculate on 
the back. 
Fifteen or twenty species are known, inhabitants of fresh 
water in all parts of the world, both in the tropics and the frigid 
zone. ‘ 
Twelve species occur in North America, which may be briefly 
characterized as follows: 
Carpels smooth. 
Flowers on emersed spikes. 
Floral leaves shorter than the flowers, Spikes nearly 
naked, 
Flowers in verticils. 1. MW. spicatum. 
Flowers alternate, or subverticillate below. 
; 2. M. alterniflorum. 
Floral leaves longer than the flowers, pectinate-pinnatifid. 
3. MW. verticillatum. 
