6l2 



TRAPACEAE. 



VOL. II. 



i. Trapa natans L Swimming Water- 

 nut. Water-Caltrop. Fig. 3076. 



Trapa natans L. Sp. PI. 120. 1753. 



Rooting in the mud at the bottom of lakes 

 or slow streams ; stem often several feet long. 

 Submerged leaves approximate, pectinately 

 dissected, i'-4' long; floating leaves in a 

 rosette sometimes i broad, their blades 

 rhombic-ovate, sharply dentate above, broadly 

 cuneate and entire below, about i' wide, gla- 

 brous and shining above, the conspicuous veins 

 of the lower surface beset with short stiff 

 hairs ; petioles of the floating leaves 2'-6' long, 

 inflated and spongy ; flowers white, about 3" 

 broad; fruit i'-2' long, armed with 4 some- 

 what recurved spines. 



Naturalized in ponds and streams, eastern Mas- 

 sachusetts, and near Schenectady, N. Y. Native 

 of Europe. Called also sanghara-nut, Jesuit's 

 water-nut. Seed mealy, edible. June-July. 



Family ioo. HALORAGIDACEAE Kl. & Garcke, Bot. Erg. Wald. 151. 1852. 



WATER- MILFOIL FAMILY. 



Perennial or rarely annual herbs, mainly aquatic, with alternate or verticillate 

 leaves, the submerged ones often pectinate-pinnatifid Flowers perfect, or monoe- 

 cious, or dioecious, axillary, in interrupted spikes, solitary or clustered. Calyx- 

 tube adnate to the ovary, its limb entire or 2-4-lobed. Petals small, 2-4, or none. 

 Stamens 1-8 Ovary ovoid-oblong, or short-cylindric, 2-8-ribbed or winged, 

 i-4-celled; styles 1-4; stigmas papillose or plumose. Fruit a nutlet, or drupe, 

 compressed, angular, ribbed or winged, indehiscent, of 2-4 i-seeded carpels. 

 Endosperm fleshy ; cotyledons minute. 



Eight genera and about ioo species, of wide geographic distribution. 



Stamen i ; ovary i -celled. i- Hippuris. 



Stamens 2-8 ; ovary 3-4-celled. 



Fruit 3-angled or 4 -angled. 2. Proserpmaca. 



Fruit of 4 carpels. 3- Mynophyllum. 



i. HIPPURIS L. Sp. PI. 4- 1753- 



Aquatic herbs, with simple erect stems, and verticillate simple entire leaves. Flowers 

 small, axillary, perfect, or sometimes neutral or pistillate only. Limb of the calyx minute, 

 entire. Petals none. Stamen i, inserted on the margin of the calyx. Style filiform, stig- 

 matic its whole length, lying in a groove of the anther. 

 Fruit a small i-celled i-seeded drupe. [Greek, mare's-tail.] 



Three known species, natives of the north temperate and 

 arctic zone and of southern South America. Besides the 2 

 following, the third occurs in northwestern arctic America. 

 Type species : Hippuris vulgaris L. 



Leaves linear or lanceolate, in verticils of 5-12. i. H. vulgaris. 

 Leaves obovate, oblong, or oblanceolate,^n verticils of 4-6. 



2. H. tetraphylla, 



i. Hippuris vulgaris L. Bottle Brush. Mare's- 

 tail. Joint-weed. Fig. 3077. 



Hippuris vidgaris L. Sp. PI. 4. 1753. 



Stem slender, glabrous, 8'-2o' high. Leaves linear or 

 lanceolate, acute, sessile, $"-12" long, i"-2" wide, in 

 crowded verticils of 6-12, more or less sphacelate at the 

 apex ; stamens with a short thick filament, and compara- 

 tively large 2-celled anther, dehiscent by lateral slits ; seeds 

 ovoid, hollow ; stigma persistent. 



Swamps and bogs, Labrador and Greenland to Alaska, south 

 to Maine, New York, Illinois, Nebraska, in the Rocky Moun- 

 tains to New Mexico, and on the Pacific Coast to California. 

 Also in Patagonia, and in Europe and Asia. Summer. Cat's- 

 tail. Witches'-milk. Paddock-pipes. Knotgrass. 



