Low herbs with a rootstock and fibrous roots. Flowers terminal. Leaves 5 in whorl near the top of the plant. Sepals and petals separate, ascending, the former generally longer than the latter. Lip erect from the base of the column, crested, spurless, sessile. Anthers and pollinia as in Pogonia. Capsule oblong, erect. [Greek, in equal threes.]

Only the following species are known, the first being the type:

1. Isotria Verticillata (Willd.) Raf. Whorled Pogonia

Fig. 1383

Arethusa verticillata Willd. Sp. PI. 4: 81. 1805. Pogonia verticillata Nutt. Gen. 2: 192. 1818. I. verticillata Raf. Med. Rep. II. 5: 357. 1808.

Stem 10-12' high, from long fleshy roots, bearing a whorl of 5 leaves at the summit. Leaves obovate, abruptly pointed at the apex, sessile, 1-3' long; flower solitary, erect or declined; peduncle 6"-8" long, in fruit usually equalling or exceeding the capsule; sepals linear, 1 1/2'-2' long, about 1" wide, spreading, dark purple; petals linear, erect, obtuse, greenish yellow, about 10" long; lip 3-lobed, crested along a narrow band, the upper part expanded, undulate; capsule erect, 1' or more long.

In moist woods, Ontario to Massachusetts, Indiana, Michigan and Florida. Ascends to 4500 ft. in Virginia. Whorled snake-mouth. May-June.

2. Isotria Affinis (Austin) Rydb. Smaller Whorled Pogonia

Fig. 1384

Pogonia affinis Austin; A. Gray, Man. Ed. 5, 507. 1867.

I. affinis Rydb. in Britton, Man. 297. 1901.

Smaller than the preceding species, stem 8'-10' high. Leaves in a whorl of 5 at the summit, 1'-2' long; flowers 2 or solitary, greenish yellow; peduncle 2"-4" long, much shorter than the ovary and capsule; sepals equalling the petals, or but little longer, somewhat narrowed at the base; lip crested over nearly the whole face and lobes; capsule erect, 1' long or less.

In moist woods, Vermont and Massachusetts to southern New York and Pennsylvania. Rare and local. Our figure is taken from Mr. Austin's original sketches. June.