CALLITRICHACEAE. 



VOL. II. 



2. Callitriche palustris L. Vernal Water-Star- 

 wort. Water Fennel. Fig. 2770. 



Callitriche palustris L. Sp. PI. 969. 1753. 



Callitriche verna L. Fl. Suec. Ed. 2, 4. 1755. 



Callitriche vernalis Koch, Syn. Fl. Germ. Ed. 2, 245. 1837. 



Aquatic or growing in the mud, stems 2 r -io' long. Sub- 

 merged leaves linear, i-nerved, retuse or bifid at the apex, 

 5"-io" long ; emersed or floating leaves obovate, obtuse, 

 truncate or retuse at the apex, narrowed at the base into 

 a margined petiole, dotted with stellate scales ; aquatic 

 forms occur with the leaves all linear; fruit 2-bracted, 

 oval, 4"-i" long, about one-half as broad, nearly flat on 

 the face, slightly notched at the apex, winged only toward 

 the apex, or all around, separated by a deep groove. 



__ Mostly in cold or running water, apparently occurring nearly 



throughout the United States and Canada. Also in South 

 America, Europe and Asia. Water-chickweed. July-Sept. 



3. Callitriche heterophylla Pursh. Larger 

 Water-Starwort. Fig. 2771. 



Callitriche heterophylla Pursh, Fl. Am. Sept. 3. 1814. 



Similar to the preceding species, either aquatic or grow- 

 ing in the mud. Fruit smaller, mostly obovate, usually 

 slightly less than \" long, and about the same breadth, 

 broadly notched at the apex, thick, plano-convex, almost 

 ventricose at the base; lobes obtusely angled with a small 

 intervening groove, wingless, or with a narrow wing or 

 raised border on the margins; styles usually longer than 

 the fruit, erect. 



In ponds and slow streams, Newfoundland to Manitoba, 

 Florida, Missouri, Colorado and Louisiana. July-Sept. 



4. Callitriche autumnalis L. 

 Northern Water-Starwort. 



Autumnal or 

 Fig. 2772. 



Callitriche palustris var. bifida L. Sp. PI. 696. 1753. 

 Callitriche autumnalis L. Fl. Suec. Ed. 2, 4. 1755. 

 Callitriche bifida Morong, Mem. Torr. Club 5: 215. 1894. 



Entirely submerged. Leaves crowded, linear or linear- 

 lanceolate, clasping at the base, retuse or bifid at the 

 apex, i-nerved, s"-8" long, without stellate scales ; fruit 

 sessile, or rarely minutely pedunculate, orbicular or 

 slightly narrower than long, $"-i" in diameter, its lobes 

 separated by a deep groove and broadly winged on the 

 margins ; styles as long as the fruit, or shorter, soon 

 deciduous ; bracts none. 



In flowing water, Quebec and Lake Champlain to Michigan, 

 Manitoba and Oregon, south in the Rocky Mountains to Colo- 

 rado. Also in Europe and Asia. July-Sept. 



Family 72. EMPETRACEAE Dumort. Fl. Belg. 106. 1827. 



CROWBERRY FAMILY. 



Low evergreen shrubs, with small narrow nearly sessile exstipulate leaves 

 jointed to short pulvini, channeled on the lower side by the revolute margins, 

 and small dioecious or rerely polygamous flowers, axillary or in terminal heads. 

 Calyx of 3 sepals. Corolla or 2 or 3 petals, or none. Staminate flowers with 

 2-4 (mostly 3) stamens, the filaments filiform, the anthers 2-celled, longitudi- 

 nally dehiscent, sometimes with a rudimentary pistil. Pistillate flowers with a 

 2-several-celled sessile ovary, the single style cleft into as many stigma-bearing 

 segments as there are ovary-cavities ; ovules i in each cavity, amphitropous. 

 Fruit a berry-like drupe, containing 2-several i-seeded nutlets. Embryo 

 straight, terete, in copious endosperm. 



Three known genera, the following, and the monotypic Ceratiola of the southeastern United 

 States. 



Flowers axillary ; petals 3. 



Flowers in terminal heads ; petals none. 



1. Empetrum. 



2. Corema. 



