432 HALORAGIDACEAE 
Leaves alternate, toothed or finely dissected. Flowers in the leaf axils, 
small, without petals. Stamens 3; pistils 3. Fruit long, 3- or 4-celled. 
1. P. palustris, L. (Fig. 9, pl. 105.) Mrrmatp-wreep. Aquatic. 
Plant from } to 2 ft. long. Leaves which float are narrow lance-shaped or 
elliptic, with sharp serrations. Those submersed are finely feather- 
formed. Common in swamps. June-July. 
2. P. pectinata, Lam. (Fig. 10, pl. 105.) CuT-LEAVED MERMAID- 
WEED. Aquatic. Leaves all finely feather-formed. Otherwise much like 
the former species. Plant 5 to 10 in. long. Rare in our section. Swamps. 
3. MYRIOPHYLLUM, L. 
Aquatic herbs, with creeping roots; leaves in whorls or alternate and 
with greenish flowers, Leaves, which are wholly under water, are dis- 
sected into capillary segments, those above toothed or with smooth bor- 
ders. The upper flowers are generally stamen bearers, those below are 
pistillate. Petals none, calyx 4-toothed. Stamens 4 to 8. Some of the 
flowers have both stamens and pistils. Fruit of 4 nut-like hard carpels, 
which are coherent at their angles. 
Flowers in narrow spikes above the submersed_ leaves. 
Leaves of the flower spike very small; flowers in whorls . . M. spicatum 
Leaves of the flower spike longer than the flowers and much dissected; 
submersed leaves in dense whorls, stamens 8 . a MG verticillatum 
Plant nearly leafless, the leaves being reduced to small bract- or hair-like 
appendages, stamens 4 - « « MM. tenellum 
Flowers on both submersed and emersed | parts ‘of ‘the plant. 
Plant with a few scattered leaves, those of the upper part linear, those 
of the lower part feather- formed, dissected; stamens 4 . M. humile 
Leaves of flower bearing portion of stem in whorls of 4 or 5, not “thread- 
like, with conspicuous teeth; stamens 4. 
Flowers alternate Le ae tet wien fe Sau ee Mes pou ee ieee een cre 
Floral leaves linear . - «© »« « M, scabratum 
Floral leaves lance- shaped or egg- ‘shaped - . « M. heterophyllum 
Flowers only on spikes which are submersed . ~ °°. «©  « Wh Parbetin 
1, M. spicatum, L. (Fig. 4, pl. 105.) Sprkep WATER-MILFOIL. 
Plant, growing in deep water, the submersed leaves finely dissected into 
capillary segments, in whorls of 4 or 5 leaves. At the summit is a long 
spike with whorls of inconspicuous greenish flowers which are accompanied 
or not by leaves reduced to bracts, which are shorter than the small 
flowers. Stamens 8. In ponds and quiet waters. 
2. M. alterniflorum, DC. Loose-rrowErRED WATER-MILFOIL. Sub- 
mersed leaves finely feather-formed. Flowers alternate. Ponds, lakes and 
streams, Mass. and Lake Champlain. 
3. M. verticillatum, L. (Fig. 5, pl. 105.) Wuortep WATER-MILFOIL. 
Plant of deep or shallow water. The arrangement of submersed leaves 
similar to that of No. 1. The floral leaves are conspicuous and like those 
under water are finely dissected. Stamens 8. 
4. M. tenellum, Bigel. (Fig. 2, pl. 105.) SLENDER WATER-MILFOIL. 
Plant, growing mostly at borders of ponds, 3 to 10 in. high, Stems nearly 
leafless, or with very small capillary appendages. Flowers in a spike on 
upper part of stem. Stamens 4. 
5. M. humile, (Raf.) Morong. (Fig. 3, @ and Bb, pl. 105.) Low 
Warer-MILrort. Plant of ponds and ditches. The form growing in mud, 
out of water, Fig. 3, b., about 1 to 2 in, high, with the upper leaves, 
