268 LVI. LOASACE^. Mentzelia. 



thick, branching. Leaves very various, lowest floral ones pectinately divided. 

 Petals somewhat persistent. Sepals minute. Bracteoles serrulate. Jn. — Sept. 



4. M. AMBiGUUM. Nutt. (M. natans. DC.) Water Milfoil. 



Ia>s. alternate, submersed ones pinnate, with capillary segments, middle 

 ones pectinate, upper linear, petiolate, toothed or entire ; Jls. mostly ^ ; pet. ob- 

 long, somewhat persistent •, sta. 4 ; carpels smooth, not ridged on the back. — In 

 ponds and ditches, Penn. to Mass. ! Stems floating, upper end emerged with 

 the minute flowers, and linear floral leaves. But in other situations it varies 

 as follows : 



/?. limosum. Nutt. (M. procumbens. Bu\) — St. procumbent and rooting; 

 leaves all linear, rigid, often entire.— Muddy places ! where it is a small, creep- 

 ing and branching plant. 



y. capillaceuin. Torr. — Ijvs. all immersed and capillary. — Ponds ! 



5. M. TENELLUM. Bw. 



Erect and almost leafless; jioral Ivs. or bracts alternate, minute, entire, ob- 

 tuse ; /s. (^ ; pet. linear ; sta. 4 ; carpels smooth, not ridged. — About the edges 

 of ponds and rivers, Providence, R. I. Olney! northern part of N. Y. to New- 

 foundland. Rhizoma prostrate, creeping, sending up several stems or scapes, 

 which are simple, and 4 — 12' high. Flowers small, purplish-white, sessile, al- 

 ternate, a little shorter than the bracts, the upper ones ^. Jl. 



6. M. scABRATUM. Michx. 



Dvs. pinnatifid, in whorls of 4s and 5s ; jls. verticillate, axillary ; iipper 

 jls. (^, with 4 stamens ; lower ones 9 ; fr. 8-angled, the ridges tuberculate. — 

 Plymouth, Mass. Oakes. Block Island, Robbins, S. and W. States, Stem 6 — 

 12' high. Segments of the leaves linear-capillary. 



10. HIPPtJRIS. 



Gr. y-iTOS, a horse, oVjsa, tail. 



Calyx with a minute, ei^tire limb, crowning the ovary ; corolla ; 

 stamen 1, inserted on the margin of the calyjjt; anther 2-lobed, 

 compressed; style 1, longer than the stamen, stigmatic the whole 

 length, in a groove of the anther ; seed 1. — %■ Aquatic herbs. St. 

 simple. Lvs. verticillate, entire. Fls. axillary, minute. 



H. VULGARIS. Mare's-tail. (Fig. 45.) 



lyvs. in verticils of 8 — 12, linear, acute, smooth, entire ; fls. solitary, often 

 Q 5 (^.— In the borders of ponds and lakes, Penn. to Arctic Am., very rare. 

 Rhizoma with long, verticillate fibres. Stem erect, jointed, 1— 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, and with neither calyx, 

 lobes or corolla. May, Jn. 



Order LVI. LOASACE^.— Loasads. 



Plants herbaceous, hispid, with pungent hairs secreting an acrid juice. 

 Lvs. opposite or alternate, usualb'more or less divided. Stipziles 0. 

 Fed. axillary, l-flowered. Sep. united, 5, persistent, equal. 

 Cor —Petals 5 or 10, cucullate, inserted into the recesses of the calyx. 

 Sta. 00. inserted with the petals, distinct or adhering in several seta. 

 Ova. adherent to the calyx more or less, 1-celled, with 3—5 parietal placentae. Sty. I. 

 Sds. many or few, anatropous. 

 Genera 15, species 70, natives of Amenca. 



MENTZELIA. 



Named by Linn, in honor of C. Mentzel, physician to the Elector of Brandenburg. 



Calyx tubular, limb 5-parted ; petals 5— 10, flat, spreading ; sta- 

 mens indefinite, 30—200 ; ovary inferior ; styles 3, filiform, connate, 

 and often spirally twisted ; stigmas simple, minute ; capsule 1-celled, 

 many-seeded. — Branching herbs. Lvs. alternate. 



1. M. LiNDLEYi. Torr. & Gray, (Bartonia aurea. Lindley.) Golden Barto- 

 7iz«.— Hispid ; lvs. ovate-lanceolate, pinnatifid, lobes often dentate; fls. solitary 



