CXXI. EUPHORBIACE.E. 485 



ginate ; caps, with the lobes obtusely margined. — This little polymorphous 

 plant is common in shallow streams and muddy places, U. S. Stem floating, 

 I — 2f long, composed of 2 tubes, simple or branched. Leaves 2 at each node, 

 becoming crowded above into a star-like tuft upon the surface of the water, the 

 lower ones becoming gradually narrower, and the lowest quite linear. Flowers 

 white, axillary, 1 or 2 together, often moncEcious. Anther a little exssived, 

 yellow. May — Sept. 



0. autumnalis. Darl. (C. autumnalis. L. C. linearis. Ph.) Floating ; Ivs. 

 nearly all linear, 1-veined, truncate or emarginate, the upper ones a little di- 

 lated towards the end. — In similar situations with, and generally accompanying 

 the former. 



y. terre^tris. Darl. (C. tcrrestris. Raf. C. brevifolia. Ph.) Procumbent ar:d 

 diffuse ; lis. all oblong, obtuse, crowded, fleshy. — Grows on soft mud, ever- 

 spreading the surface. This form evidently depends on the locality. 



Order CXX. PODOSTEMACE^.— Threadfoots. 



Herbs aquatic, without spiral vessels, of the habit of the liverworts or mosses. 

 Lv8. capillary or linear, not articulated with the stem. 



F:8. moncecious, achlamydeous. bursting throug-h an irregularly lacerated spathe. 

 Sta. often reduced to 1 or 2, and monadelphous. 

 Ova. free, 2— 3-celled. Sty. 2 or 0. Stig. 2—3. 

 P/-.— Capsule subpedicellate, opening by 2 valves. 

 Sds. numerous, without albumen, attached to a central column. 

 Genera 9, spc-ies 25, natives of N. America and Asia. 



P O D O S T E M U M. L. C. Rich. 



Gr. iroi'j, 7ro(5oj, afoot, arniiov ; the stamens being apparently on a common foot-stalk. 



Stamens 2, with the filaments united below; ovary oblong-ovoid ; 

 stigmas 2, sessile, recurved ; capsule 2-celled ; seeds minute. — Small, 

 submersed herbs .^ adhering to stones and pebbles. 



P. CERATOPHYLLUM. Michx. (Lacis ceratophylla. Bongard.) Threadfoot. 



Lvs. dichotomously dissected ; Jls. solitary, axillary. — Middle ! Western 

 and Southern States. Stem a few inches long, usually destitute of roots and 

 attached to stones by lateral, fleshy processes. Leaves numerous, alternate, 

 coriaceous, divided into many long, linear-setaceous segments. Flowers on 

 short, thick peduncles, the 2 stamens and styles at length bursting through the 

 lacerated calyx. In shallow, running streams. July. 



Order CXXI. EUPHORBIACEiE.— Spurgeworts. 



Trees, shrubs or hcrb^, often abounding in an acrid milk. 



Lnn. opposite or alternate, simple, rarely compound, often furnished with stipules. 



F.n. moniKcious or diwcious, axilliirv or terminal. Cal. inferior, lobed or wanting. 



Cor.— PiUals or scales equal in number to the sepals, or wanting. 



SterUe.fl.—Sta. definite or indefinite, distinct or monadelphous. Anth,. 2-celIed. 



Fertile Jl.— Ova. free, of 2— 9 more or less united carpels, coherent to a central prolongation of the axifl. 



Styles distinct, otten 2-clefl. 

 Fr. — Capsule of 3 dehiscent carpels which open elaatically. 

 Sd. with a large embrj-o in fleshy albumen. 



Genera 191. species 2500? chiefly natives of S. America, not more than 50 species being found in N. 

 America, north of Mexico. 



Properlif^.— An iscrid, stimulant and poisonous principle, residing chiefly in the milky juice, pervades 

 the wholf- order This principle varies in activity from mild stimulants lo the mo-it active poisons; but 

 it is volatile and easily expelled jjy heat. Tapioca is a starch-like accumulation lbrme<l in the roots ot 

 tlie JatrophaManihot. When Iresh, this root is a violent poison, but lases its deleterious properties by 

 washing and e.M.osiire to heat. Cwitoroil is e.xpres.sed from the seeds of Uicinus communis. Croton- 

 oil from the seeds of Croton Tiglium. Caoutchouc is yielded in abundance by several S. American specie.?. 



FIG. 53.— 1. Head or cnpitulum of Eu- 

 hi>rbia corollal I, witli tliu . o.i>ll i-liKe in- 

 volucre, and pedicellate pi.-^lillate flower. 

 2. The involucre tube cut open, .-hownKf 

 the monandrous, staminate flowers sur- 

 roun<iing the pistillate. 3. One of the 

 flowers, with n toothed bract nt base. 1. 

 ('ross section of the ovary, showing the 3 

 one-seeded ceils or cariM,'lJi. 



