Slender Pigweed. Amaranthus hybridus L. (A. chlorostachys). Seeds smooth, highly polished, jet-black, double convex, broadly ovate, with a slight notch at the narrow extremity, 1.1–1.4 mm. long. Distinguished from the preceding species by having a seed ovate instead of circular. Introduced from tropical America. Not abundant.

Fig 58. [Rough Pigweeds. Amaranthus retroflexus] L.

Rough Pigweeds. Amaranthus retroflexus L. Sometimes incorrectly called red-root. Seeds smooth, highly polished, jet-black, double convex, broadly ovate, with a slight notch at the narrow end, .9–1.2 mm. long. The seeds of this and the next preceding are ovate, while those of the first two are very nearly circular. When seen edgewise, the hem-like margin of this seed is less prominent then in either of the preceding three noticed above. Found almost everywhere in annual crops. Introduced from tropical America.

KNOTWEED FAMILY. ILLECEBRACEAE.

Fig 59. [Knawel. Scleranthus annuus] L.

Knawel. Scleranthus annuus L. As the seed is single for each flower, it is unnecessary for the ovary to open; the small, hardened, ten-angled calyx with its five thick lobes aid in protecting and distributing the seed within. The seed is seldom seen. Calyx straw colored, obovoid, 2 mm. long besides the five spreading, membranaceous lobes, which are nearly as long. A low spreading plant, resembling some kinds of chickweed.