The Plants of Michigan Part 58

6b. Spike acute --7.

7a. Spike densely flowered, 1-2 cm. long =Milkwort, Polygala verticillata.=

7b. Spike loosely flowered, 2-5 cm. long =Milkwort, Polygala verticillata var. ambigua.=

EUPHORBIACEAE, the Spurge Family

Herbs, with alternate, opposite, or whorled leaves and usually milky juice. Flowers small or minute and inconspicuous, without petals and frequently without calyx. In our commoner species, several staminate flowers, each consisting of a single stamen only, and one pistillate flower, consisting of a single pedicelled 3-lobed ovary only, are included within a 4-5-lobed involucre, which is sometimes colored and resembles a calyx or corolla.

1a. Stem-leaves alternate; inflorescence axillary; flowers with calyx and several stamens (3-8 dm. tall; flowers greenish or purplish; summer) (Three-seeded Mercury) --2.

1b. Stem-leaves opposite, usually inequilateral at base; flowers as described for the family; apparent flowers in axillary cl.u.s.ters (summer and autumn) (Spurge) --3.

1c. Stem-leaves alternate; inflorescence a terminal umbel-like cl.u.s.ter, with its branches subtended by opposite or whorled leaves; flowers as described for the family (Spurge) --9.

2a. Leaves ovate or ovate-lanceolate; flower-cl.u.s.ters shorter than the subtending bract =Three-seeded Mercury, Acalypha virginica.=

2b. Leaves lanceolate to oblong; flower-cl.u.s.ters equaling or exceeding the subtending bract =Three-seeded Mercury, Acalypha gracilens.=

3a. Stem and foliage glabrous --4.

3b. Stem and foliage more or less p.u.b.escent (stems prostrate or ascending, 1-4 dm. long) --7.

4a. Erect or ascending, usually without basal branches (2-4 dm.

tall) =Spurge, Euphorbia preslii.=

4b. Prostrate or spreading, branched from the base (stems 1-4 dm.

long) --5.

5a. Leaves entire; plants of the sh.o.r.es of the Great Lakes =Spurge, Euphorbia polygonifolia.=

5b. Leaves serrulate --6.

6a. Leaves broadly oblong or obovate; seeds obscurely wrinkled =Spurge, Euphorbia serpyllifolia.=

6b. Leaves narrowly oblong; seeds with prominent transverse ridges =Spurge, Euphorbia glyptosperma.=

7a. Seeds black =Spurge, Euphorbia hirsuta.=

7b. Seeds red --8.

8a. Leaves oblong =Spurge, Euphorbia maculata.=

8b. Leaves elliptical to obovate; involucre split down one side =Spurge, Euphorbia humistrata.=

9a. Flowers subtended by conspicuous petal-like white appendages (part of the involucre) (4-10 dm. tall; summer) =Spurge, Euphorbia corollata.=

9b. Flowers not subtended by petal-like appendages --10.

10a. Stem-leaves below the inflorescence serrulate (2-5 dm. high; summer) --11.

10b. Stem-leaves below the inflorescence entire --13.

11a. Upper leaves acute =Spurge, Euphorbia platyphylla.=

11b. Upper leaves obtuse, rounded, or notched at the apex --12.

12a. Leaves of the involucre broadly triangular-ovate, widest near the base =Spurge, Euphorbia obtusata.=

12b. Leaves of the involucre broadly obovate to nearly circular, widest near or above the middle =Spurge, Euphorbia helioscopia.=

13a. Stem-leaves narrowly linear, less than 3 mm. wide (2-4 dm. high; late spring and summer) =Cypress Spurge, Euphorbia cyparissias.=

13b. Stem-leaves narrowly oblong-spatulate, more than 5 mm. wide, and more than 3 times as long as wide (2-6 dm. high; summer) --14.

13c. Stem-leaves obovate to nearly circular, not more than twice as long as wide (1-4 dm. high) --15.

14a. Leaves at base of umbel narrow, resembling those on the stem =Spurge, Euphorbia esula.=

14b. Leaves at base of umbel broad, resembling those of the inflorescence =Spurge, Euphorbia lucida.=

15a. Upper stem-leaves distinctly narrowed at the base; introduced species of waste places (summer) =Spurge, Euphorbia peplus.=

15b. Upper stem-leaves rounded at the sessile base; native species of woodlands (spring and early summer) =Spurge, Euphorbia commutata.=

CALLITRICHACEAE, the Water Starwort Family

Small herbs growing in water or in mud, with opposite entire leaves and small inconspicuous axillary flowers, with neither calyx nor corolla.

(Flowers in summer).

1a. Completely submerged; leaves all linear =Water Starwort, Callitriche autumnalis.=

1b. Submerged leaves linear, emersed and floating leaves obovate =Water Starwort, Callitriche pal.u.s.tris.=

EMPETRACEAE, the Crowberry Family

Low evergreen shrubs, with the linear leaves completely rolled into a tube, and inconspicuous flowers without petals, in the axils of the leaves.