The Plants of Michigan Part 61

TILIACEAE, the Linden Family

Trees, with alternate, simple, palmately veined leaves, and cl.u.s.ters of fragrant white flowers in late spring arising from the middle of a leaf-like bract; sepals and petals each 5; stamens numerous, but united into 5 sets.

One species in Michigan =Ba.s.swood, Tilia americana.=

MALVACEAE, the Mallow Family

Herbs with alternate leaves; sepals and petals each 5; stamens numerous, united by their filaments to form a tube surrounding the styles; ovary many-celled.

1a. Flowers yellow (summer and autumn) --2.

1b. Flowers pale-yellow, with a dark center (2-4 dm. high; late summer) =Flower-of-an-hour, Hibiscus trionum.=

1c. Flowers white to red or blue, never yellow --3.

2a. Leaves broadly heart-shape (10-15 dm. tall) =Velvet Leaf, Abutilon theophrasti.=

2b. Leaves ovate-lanceolate (2-5 dm. tall) =Sida, Sida spinosa.=

3a. Calyx subtended by 6 to many bractlets which are sometimes united at base (summer) --4.

3b. Calyx subtended by 3 bractlets, or by none --6.

4a. Flowers 2-4 cm. wide (5-10 dm. high; flowers pink) =Marsh Mallow, Althaea officinalis.=

4b. Flowers 7-15 cm. wide (8-15 dm. high; flowers pink to nearly white) (Rose Mallow) --5.

5a. Leaves densely p.u.b.escent below =Rose Mallow, Hibiscus moscheutos.=

5b. Leaves glabrous =Rose Mallow, Hibiscus militaris.=

6a. Petals prominently notched at the end or reverse heart-shape (Mallow) --7.

6b. Petals obtuse or truncate (summer) --11.

7a. Flowers 1-1.5 cm. wide --8.

7b. Flowers 2-5 cm. wide (3-8 dm. high; flowers in summer) --9.

8a. Stems proc.u.mbent, prostrate, or spreading (spring, summer, and autumn) =Mallow, Malva rotundifolia.=

8b. Stems erect (10-15 dm. high; summer) =Mallow, Malva verticillata.=

9a. Leaves with prominent but shallow lobes; flowers axillary =Mallow, Malva sylvestris.=

9b. Leaves deeply lobed or cleft; flowers in the upper axils, producing a raceme-like cl.u.s.ter --10.

10a. Lobes of the leaf dentate or incised =Mallow, Malva alcea.=

10b. Lobes of the leaf pinnately cleft into linear or narrowly oblong divisions =Mallow, Malva moschata.=

11a. Flowers white (1-2 m. high) =Virginia Mallow, Sida hermaphrodita.=

11b. Flowers purple or pink (3-5 dm. high, spreading) =Poppy Mallow, Callirhoe triangulata.=

HYPERICACEAE, the St. John's-wort Family

Herbs or shrubs, with opposite entire leaves dotted with translucent glands; flowers usually yellow (or pink); sepals and petals each 5; stamens 5 to many; ovary with 3-5 styles. (St. John's-wort.)

1a. Shrubs (4-8 dm. high; flowers yellow, summer) --2.

1b. Herbs (flowers in summer) --3.

2a. Styles 5 =St. John's-wort, Hyperic.u.m kalmianum.=

2b. Styles 3 =St. John's-wort, Hyperic.u.m prolific.u.m.=

3a. Flowers pinkish, 15 mm. broad (3-5 dm. high, in swamps) =Marsh St. John's-wort, Hyperic.u.m virginic.u.m.=

3b. Flowers yellow --4.

4a. Flowers about 4 cm. wide; princ.i.p.al leaves 5-10 cm. long (7-15 dm. tall) =St. John's-wort, Hyperic.u.m ascyron.=

4b. Flowers 8-25 mm. wide; stamens 15 or more --5.

4c. Flowers 1-10 mm. wide; stamens 12 or fewer (1-6 dm. high) --7.

5a. Petals dotted with black (4-8 dm. high) --6.

5b. Petals without black dots (2-5 dm. high) =St. John's-wort, Hyperic.u.m elliptic.u.m.=

6a. Flowers 20-25 mm. wide; leaves of an oblong type, broadest near the middle =St. John's-wort, Hyperic.u.m perforatum.=

6b. Flowers 10-15 mm. wide; leaves of an ovate type, broadest below the middle =St. John's-wort, Hyperic.u.m punctatum.=

7a. Leaves minute, subulate, 1-3 mm. long =Pineweed, Hyperic.u.m gentianoides.=

7b. Leaves linear, with 1-3 princ.i.p.al veins, broadest near or above the middle =St. John's-wort, Hyperic.u.m canadense.=