522 ORDER CXXII. ORCHIDACEJE. 



florets with a 2-leaved spathe. Styles 6, 2 -cleft. Capsule 5- 

 celled, many-seeded. 



1. H. spongio'sa, (Bore.) Leaves floating, orbicular, cordate, with 

 purple veins beneath, with inflated vessels near the summit of the stem. 

 Flowers axillary. Styles 6, deeply 2-cleft. Stigma simple, spotted. 

 Seed numerous, striate. — White, tinged with purple. 2£. July — Sept. 

 Stagnant waters. 



Genus II.— VALLISNE'RIA. Mich. 20—2. 

 (In honor of Antonio Yallisneri, an Italian botanist.) 



Flowers dioecious. 'Sterile florets ; spathe 2 — 4-parted ; spa- 

 dix covered with minute flowers ; sepals 3 ; stamens 2. Fer- 

 tile flowers; scape spiral, very long ; spathe 2-cleft; sepals 3, 

 elongated; petals 3, smaller than the sepals; stigmas 3, sessile; 

 capsule cylindrical, 1-celled, many-seeded, 3-toothed. 



1. V. spira'lis, (L.) A floating plant. Leaves linear, obtuse, 8- 

 nerved, minutely serrulate. Scapes axillary; those bearing the sterile 

 flowers very short, the fertile ones long and spiral, raising the flowers 

 to the surface of the water when ready to expand. — White. If. Aug. 

 — Sept. Tape-weed. Eel-grass. 



Order CXXII.— ORCHID A'CEJS. (Orchis Family.) 



Perianth superior, ringent, 6-parted ; the 3 outer segments 

 colored, the odd one uppermost, from the twisting of the ovary ; 

 the 3 inner colored, with the odd one below, which is frequently 

 lobed and different from the others, often spurred. Stamens 3, 

 united into a central column, epigynous, the two lateral ones 

 usually abortive. Pollen powdery, or in waxen masses. Ovary 

 usually 1-celled, with 3 parietal placentae ; ovules numerous. 

 Style forming a part of the column with the stamens. Stigma 

 a viscid cavity in front of the column. Fruit usually an infe- 

 rior capsule, rarely baccate. Seeds numerous. Albumen none. 

 Herbaceous plants, usually with tuberous roots. Leaves simple, 

 entire. 



ANALYSIS. 



1. Lip spurred or saccate 2 



Lip not spurred 5 



2. Lip saccate Cypripedium, 15 



Lip spurred 8 



3. Spur joined to the ovary Corollorhiza, 7 



Spur free 4 



4. Lip entire ; racemes not leafy Tipularia, 12 



Lip entire ; racemes leafy Orclt to, 10 



Lip not entire Habenaria, 11 



5. Flowers solitary 6 



Flowers several or numerous 7 



6. Stems sheathed .Arethusa, 8 



Stems with one or more leaves Pogonia, 6 



