4 M. scabratum Mx. Lvs. pinnatifid in whorls of 4s and 5s; fls. verticillate, axillary, upper fls.Order LII Onagraceae Onagrads Part 6 695 , with 4 stam., lower ones Order LII Onagraceae Onagrads Part 6 696 ; floral lvs. linear, pectinately toothed; fr. 8-angled, the ridges tuberculate. - Plymouth, Mass. (Oak(s), Block Island (Robbins), S. and W. States. St. 6 to 12' high. Segm. of the lvs. linear-capillary.

5 M. tenellum Bw. Erect and almost leafless; floral lvs. or bracts alternate, minute, entire, obtuse; fls.Order LII Onagraceae Onagrads Part 6 697 ; petals linear; stam. 4; carp. smooth, not ridged-- About the edges of ponds and rivers, Providence, R. I. (Olney), northern part of

N. Y. to Newfoundland. Rhizome prostrate, creeping, sending up several stems or scapes which are simple and 4 to 12' high. Fls. small, purplish white, sessile, alternate, a little shorter than the bracts, the upper onesOrder LII Onagraceae Onagrads Part 6 698 . Jl. 6 M. ambiguum Nutt. Lvs. many, submersed ones pinnate, with capillary segments, middle ones pectinate, upper linear, petiolate, toothed or entire; fls. mostly Order LII Onagraceae Onagrads Part 6 699 ; petals oblong, somewhat persistent; stam. 4; carpels smooth, not ridged on the back. - In ponds and ditches, Penn. to Mass. Sts. floating, upper end emerged, with ininute fls. and linear floral lvs. (M. natans DC.) In other situations it varies as follows.

β. limosum Nutt. St. procumbent and rooting; lvs. all linear, rigid, often en tire. - Muddy places, where it is a small, creeping and branching plant. (M. procumbens Bw.)Order LII Onagraceae Onagrads Part 6 700 gapillaceum Torr. Lvs. all immersed and capillary. - Ponds.

11. HIPPU'RIS, L. Mare's Tail. (Gr.Order LII Onagraceae Onagrads Part 6 701 a horse, Order LII Onagraceae Onagrads Part 6 702 a tail.)

Calyx with a minute, entire limb crowning the ovary; corolla none; stamen 1, inserted on the margin of the calyx; anther 2-lobed, compressed; style 1, longer than the stamen, stigmatic the whole length in a groove of the anther; seed 1.-Order LII Onagraceae Onagrads Part 6 703 Aquatic herbs. St. simple. Lvs. verticillate, entire. Fls. axillary, minute.

H. vulgaris L. Lvs. in verticils of 8 to 12, linear, acute, smooth, entire; fls. solitary, oftenOrder LII Onagraceae Onagrads Part 6 704 . - In the borders of ponds and lakes, Penn. to Arc. Am., very rare. Rhizome with long, verticillate fibers. St. erect, jointed, 1 to 2f high. The flowers are the simplest in structure of all that are called perfect, consisting merely of 1 stamen, 1 pistil, 1 seed in a 1-celled ovary, with neither calyx lobes nor corolla. May, Jn.