bract; stominate flowers 6 to 20 per spike, sessile; calyx 5-lobed, the lobes about 

 1 mm. long; petals spatulate-lanceolate, obtuse, slightly exceeding the calyx; andro- 

 phore columnar, bearing two whorls of short stamens and prolonged above the 

 upper whorl; stamens short, about 5 in each whorl; pistillate flowers 1 to 6 per 

 spike, essentially sessile; calyx deeply and unequally 6-parted, with 3 longer (2-3 

 mm. long) lobes opposite the carpels and 3 shorter ones opposite the petals, all the 

 lobes acute, the whole calyx glandular-setulose on the exterior; petals 5 or 6. shorter 

 than the longer calyx lobes, whitish, clawed, caducous soon after anthesis; disk 

 absent; ovary tricoccous, densely glandular-setulose; styles 3, laminar, each about 

 4- or 5-lobed about half the length; capsule deeply tricoccous, about 4 mm. high 

 and 6 mm. broad, loculicidal and septicidal; columella short; seeds about 3 mm. 

 long, nearly spherical, foveolate. 



Frequent in rice fields, ditches and other marshy areas, s.e. Tex. (Harris, Jeffer- 

 son and Matagorda cos.), July-Oct.; widespread in warmer parts of Am., s. to 

 Parag. and n. to Tex., La. and Fla. The species arrived in Tex. about 1920. 



Fam. 79. Callitrichaceae Link Water-starwort Family 



Aquatic or terrestrial annual or perennial herbs with delicate stems, monoecious 

 or rarely dioecious; leaves opposite, entire, without stipules; flowers unisexual, 

 the perianth lacking, each flower subtended by a pair of falciform or obliquely oval 

 bracteoles (or these wanting); staminate flowers 1 to 3 in the axil of a foliage leaf, 

 consisting of a single anther on a slender filament; pistillate flowers 1 or rarely 

 more, similarly placed, composed of a single pistil of 2 carpels; styles 2, slender, 

 often much longer than the ovary; carpels splitting at maturity and usually forming 

 a fruit of 4 achenelike mericarps; mericarps flattened, winged, margined or smooth, 

 each bearing 1 seed. 



A monotypic family. 



1. Callitriche L. Water-starwort. Water-chickweed 



Characters of the family. A group of highly polymorphic species due to apomixis 

 in many of the species and to variations and different outward appearances result- 

 ing from the same species inhabiting diverse habitats, either amphibious or terres- 

 trial. 



About 40 species distributed throughout the world. 



The broad, floating leaves of most species, that arise from slender, rooted stems 

 provided with linear submersed leaves, form mats on the surface of water and 

 provide cover for fish and for some of their food population. Ducks have been 

 observed to eat the seeds and herbage. The often winged, suberous covered 

 mericarps are ideally suited for dispersal by water. 



1. Leaves dark-bright-green, linear-lanceolate, narrowed to a clasping base, the 

 base not connected by a wing, all submersed; faces of mericarps 

 obscurely and irregularly pitted 1. C. hermaphroditica. 



1. Leaves bright green, of various shapes; nodes with a narrow membranous wing 

 connecting the leaf-bases; faces of mericarps usually reticulate; 

 plants submersed or on mud (2) 



2(1). Fruit as high as wide or a little higher, rarely slightly wider than high; 

 stigmas to 6 mm. long; stamens elongating to 1.5-3 mm. as the fruit 

 matures; anthers to 1.5 mm. wide; flowers with 2 whitish inflated 

 bracteoles at base; leaves of various types on different or the same 

 plant; plant amphibious, growing entirely submersed or with a 

 terminal rosette of floating leaves, or as a mat on mud (3) 



1085 



