42 
Twentieth class. 
Cl. 20. Gynandria. 
1. Stas 6. Perianth gamopetalous, tubular, the limb cut 
obliquely into a ligule. Ls deeply cordate. FIs in the 
l.-axils.Aristolochia. 499. 
— Stas 1—2. Perianth with 6 divisions; 1 division of the 
inner circle (the lip) gen. twisted down by the torsion 
of the ovary, often of peculiar form. Orchidacece 2 
2. Pis with no green ls ...... 3 
— Pis with green ls ....... 6* 
3. Lip prolonged to a spur ..... 4 
— Lip not spurred ....... 5 
4. Spur inflated, short, pointed upwards. Lip placed above 
Epipogon. 553. 
— Spur subulate, pointed downwards. Lip placed below 
Limodorum. 554. 
5. Lip 2-lobed at the extremity . . Neottia. 558. 
— Lip undiv. at the extremity . . Corallorhiza. 561. 
6(2). Lip with a (sometimes short) spur Orchis. 541. 
— Lip not spurred ....... 7 
7. Pis having at their base 2 (rarely 1 or more than 2) 
entire, globular or oval, or compressed-palmatipartite, 
or cylindric-napiform tubers . .... H 
— Pis without subterranean tubers, but the stem bearing 
at its base a green, lateral tubercle. (FIs small, 
greenish) ........ 12 
— Pis without tubers. Root formed of branched or fascicled 
fibres (not noticeably thickened) . . . 13 
8. Lip with a 2-jointed knee, the foremost joint broken 
back. (Only in Tessin) .... Serapias. 551. 
— Lip not jointed ....... 9 
9. Stem and spike pubescent. Spike unilateral, twisted 
spirally. (FIs white) .... Spiranthes. 560. 
— Stem and spike glabrous ..... 10 
10. Divisions of the perianth all divergent. FI. of a peculiar, 
insect-like form, lip velvety brown . Ophrys. 548. 
— Divisions of the perianth all (except the lip) connivent 
11 
11. Lip stretched out, deeply 3-fid . . Herminium. 551. 
— Lip drooping, 4-lobed .... Aceras. 550. 
— Lip drooping, undiv., only with a tooth on each side 
Chamaeorchis. 549. 
12 (7). Lip obtuse, as long as the other divisions of the 
perianth.. Sturmia. 562. 
— Lip acute, shorter than the outer divisions of the perianth 
Melaxis. 563. 
13 (7). Stem with 2 opp. ls. Rad. ls 0. FIs greenish 
Listera. 557. 
