170 CALLITRICHACE^. Callitrichb. 



Ord. XCIV. CALLITRICHACEiE. Link. The Water-Chickweed Tribe. 



Flowers perfect, or sometimes by abortion moncBcious or polygamous, destitute 

 of both calyx and corolla, with a 2-leaved involucre, or naked at the base. 

 Stamens single (or rarely 2), with an elongated slender filament and reniform 

 one-celled? anther. Ovary 4-lobed, 4-celled, with a solitary ovule in each 

 cell : styles 2, spreading. Fruit laterally compressed, 4-celled and 4-seeded, 

 indehiscent. Embryo straight, in the axis of fleshy albumen. — Aquatic slender 

 annual plants, with opposite entire leaves, and minute solitary axillary sessile 

 flowers. 



1. CALLITRICHE. Linn. ; Endl. gen. 1830. water CHICKWEED. 



[ From the Greek, kajlos, beauUful, and thria, hair ; in allusion to the slender stems.] 

 Character that of the order. 



1. Callitriche verna, Linn. Common Water Chickweed. 



Leaves 3-nerved ; upper ones aggregated, broader ; fruit sessile, wilh 2 bracts at the base, 

 each carpel bluntly keeled on the back. — Linn. sp. 1. p. 6 ; Michx.Jl. 1. p. 2 ; Nutt. gen. 1. 

 p. 3 ; Arn. in Edinh. jour. nat. <^ geogr. sc. 1. p. 426 ; DC. prodr. 3. p. 70. C. aquatica, 

 Smith in Engl hot. t. 722 ; Bigel. fi. Bost. p. 2. 



var. 1. vulgaris : leaves all elongated and obovate. — DC. I. c. 



var. 2. intermedia : upper leaves spatulate-obovate ; lower ones linear. — Hoff. fl. Germ. 

 p. 2, ex DC. I. c. ; Torr. fl. 1. p. 3 ; Beck, hot p. 123 ; Darlingt. fl. Cest. p.\. C. inter- 

 media, Willd. sp. 1. p. 29 ; Pers. syn. 1. p. 6. C. heterophylla, Pursh, fl. 1. p. 3 ; Ell. 

 sk. 1. p. 4. 



var. 3. linearis: leaves all linear, or the upper ones linear -elliptical. — DC. I. c. C. 

 autumnalis, Michx. fl. 1. p. 2; Torr. I. c, not of Linn. C. linearis, Pursh, I. c. 



var. 4. terrestris : stem procumbent, rooting in mud or moist earth ; leaves closely ap- 

 proximated, linear-oblong or elliptical-oblong. — C. terrestris, Raf. in med. repos. 11. p. 358 ; 

 Torr. fl. I. p. i; DC. I. c. C. brevifolia, Pursh, I. c. C. verna, var. caespitosa, DC. I. c? 



Stem very slender, varying in length with the depth of the water (the var. terrestris growing 

 in patches, and resembling moss), consisting of two tubes, nearly simple. Uppermost leaves 

 in var. 1. and 2. more or less obovate, crowded into a stellate tuft, and floating on the surface 

 of the water ; the rest diminishing in breadth downward, till they are quite linear. Flowers 

 very minute, particularly those in the upper part of the stem. Bracts oblong, incurved, white. 

 Stamens lateral, next the stem, finally 2-4 times as long as the ovary : anther 4-celled ? 

 Ovary 4-sided : styles subulate, distinct. Fruit consisting of four oblong carpels, united in 

 pairs, so as to form two flattened disks, with a groove between them. 



