FLORA 07 THE DISTRICT OP COLUMBIA. 45
S. SOBGHASTBTJM
I. NYMPHAEA
1. PHYLLANTHTTS L
FLORA. OF THE DISTRICT OF COLUMBIA. 195
Glands of the involucre without petal-like appendages; cyathia in umbels or cymes topping a well-developed stem.
Plants annual, hairy; stipules glandlike; cyathia in cymose clusters, with 1 or rarely 4 glands 6. POINSETTIA.
Plants perennials or winter annuals, glabrous; stipules none; cyathia in 3-many- rayed umbels, with 4 glands 7. TITHYHALTJS.
Glands with petal-like appendages, or the cyathia borne in the forks of the stem near the ground.
Plants deep-rooted perennials; stipules minute 6. TITHYMALOPSIS.
Plants annuals; stipules triangular or awl-shaped 4. CHAMAESYCE.
196 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM.
3. Chamaesyce prcslii (Guss.) Arth.
Common in cultivated fields and open waste places. May-Oct. Eastern N. Amer.
(Euphorbia hyperici/olia of Ward's Flora; E. preslii Guse.) The whole plant turns crimson in autumn.
Diehropkyllum marginatum (Pursh) Klotzsch & Garcke, Bnow-on-the-mountain, is sometimes found around gardens where it has been cultivated. Native of the western U. S. (Euphorbia marginata Pursh.)
8. TTTHTMALOPSIS Klotzsch & Garcke.
The species of this genus, while generally distinct, often hybridize when they occur together, and it is probable that the great variety of occasional intermediates, even between such distinct species as T. corollata and T. ipecacuanhae, have arisen in this way. The flowers are often replaced by a cauliflower-like gall. All the species vary greatly in amount of pubescence, red color of stem and leaves, and form of leaf and appendages.
Main stem well developed, longer than the umbel; plants flowering in summer.
Leaves bright green, not much paler on the lower side, sessile or nearly so.
5. T. corollata.
Leaves dark green above, paler on the lower side, generally short-petioled, spreading or drooping. Plant more pubescent, especially at the nodes. .4. T. paniculate.
Main stem nearly always shorter than the umbel, often subterranean; plants flowering in spring or early summer.
Appendages of the involucral glands none or about half the width of the gland,
" greenish. Plant entirely glabrous or very rarely with a few hairs at the nodes;
main stem below ground, the first flowers appearing at the surface.
1. T. ipecacuanhae.
Appendages conspicuous, petal-like.
Plants with a main stem 10-30 cm. long, the stems erect, often hairy at the nodes;
leaves lanceolate to ovate or, if oblong, broadest below the middle, darker on the upper side; first flowers May to June 3. T, zlnniiflora.
Plants branching from near the ground or, if with a longer main stem, then ascend- ing, not conspicuously more hairy at the nodes; leaves of many forms, not much darker above; first flowers April to May 2. T. marylandloa.
1. Tithymalopsis ipecacuanhae (L.) Small. Wild ipbcao.
Common in open places in the sandy soils east of Washington. Apr .-May. Eastern T7. S. (Euphorbia ipecacuanhae L.)
Very variable in leaf form and color.
S. Tithymalopsls marylandlca (Greene) Small.
Rare in sandy land at Sunnyside and Seat Pleasant, but more frequent north of our range toward Baltimore. May-July. (Euphorbia arundelana Bartlett; E. mary- landica Greene.)
A great many forms intermediate between T. ipecacuanhae and T. corollata are included under this name, and it is possible that they all originated from crosses of those species, as both occur with T. marylandica in nearly every place where it hap been found.
Tithymalopsis mercurialina (Michx.) Small has been reported from our region but probably erroneously. (Euphorbia mercurialina Michx.)
8. Tithymalopsls zlnniiflora Small.
Rare in sandy land; College Park. June. Southeastern U. S.
4. Tithymalopsls paniculate (£11.) Small.
Occasional, generally in sandy land; Plum mere Island and Bladensburg, South- eastern U. S. (Euphorbia paniculata Ell.)
Specimens collected by Dewey at Glen Carlyn and by Knowlton at Laurel are intermediate between this and T. corollata.
FLORA OF THE DISTRICT OF COLUMBIA. 197
6. Tithymalopsis corollata (L.) Elotzsch & Garcke. Flowering spurge.
Common in somewhat dry open places, roadsides, and fields. July-Oct. Eastern N. Amer. {Euphorbia corollata L.)
Variable in form of leaf, inflorescence, and appendages, and in amount of pubes- cence.
6. POINSETTIA Graham.
The poinsettia (P. pulcherrima Graham), with brilliant red upper leaves,is a well- known houseplant, especially popular at Christmas time.
1. Poinsettia dentata (Michx.) Small.
Open places; Seven Locks and near Plummers Island. July-Sept. Pa. to Tex.
(Euphorbia dentata Michx.)
*
7. TITHYMALUS Adans.
The name spurge is applied generally to all the plants of this and even related genera, but more strictly belongs to T. lathymz (L.) Hill, known also as caper,spurge and mole plant, a stout glaucous plant with linear-lanceolate leaves, sometimes cultivated in gardens.
Leaves serrulate; glands transversely oval; seeds lenticular, smooth or faintly reticu- late. Winter annual; umbel 3-rayed; capsule warty 1. T. obtuaatas.
Leaves entire; glands crescent-shaped; seeds ovoid.
Leaves obovate; umbel 3-rayed; seeds pitted; winter annual 2. T. commutatus.
Leaves linear; umbel many-rayed; seeds smooth; perennial by buds on horizontal roots 3, T. eyparissias.
1. Tithymalus obtusatus (Purah) Klotzsch & Garcke.
Frequent locally in moist open woods. March-June. Eastern and southern U. S:
(Euphorbia obtusata Pursh; E. dictyosperma of Ward's Flora.)
8. Tithymalus commutatus (Engelm.) Klotzsch & Garcke.
Occasional in rich moist land, chiefly in woods, along the upper Potomac. March- June. Eastern and southern IT, S. (Euphorbia commutata Engelm.)
3. Tithymalus eyparissias (L.) Hill. Cypress sptjrgb.
One colony on the campus at College Park; also found along the railroad near Laurel. May. Cultivated from Eur. and frequently naturalized in the northeastern states. (Euphorbia q/parissias L.)
Seeds rarely in the United States but commonly at College Park.
91. CALLITRICHACEAE. Water starwort Family.
1. CALLITBICHE L. Water starwort.
Plants forming low tufts on moist soil; leaves uniform in shape, 3-nerved, crowded;
fruit pedunculate. Bracts none 1. C. austinl.
Plants aquatic or sometimes growing on mud; leaves 1-nerved; fruit sessile.
Fruit with rather fugacious bracts at the base; emersed and submersed leaves unlike.
Fruit oval, flat on the face, longer than the styles 2. C. palustris.
Fruit obovate, plano-convex, shorter than the styles 8. C. heterophylla.
Fruit without bracts; all leaves submersed, linear 4. C. autumnalis.
1. Callitriche austini Engelm.
Occasional in damp shaded places. Fr. May-June. Eastern U. S.
2. Callitrlche palustris L.
In shallow, usually running water. Fr. May-Aug. Cosmopolitan. (C+ vtma L.) 8. Callitriche heterophylla Pursh.
In shallow water; Woodside and Hunting Creek. Fr. May-Aug. Eastern U. S.
4. Callitriche autumnalis L.
In shallow water; Great Falls, Md., May, 1899 (Steele). Widely distributed in N, Amer., Eur., and Asia. (C, bifida Morong.)