This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Glabrous slender erect branching annuals, the branches often nearly filiform, with finely dissected petioled leaves, the leaf-segments very narrowly linear. Flowers very small, white, in compound unequal-rayed umbels. Involucre none; involucels of a few small narrow bracts, or none. Calyx-teeth obsolete. Fruit ovate, laterally flattened, tuberculate or bristly; ribs prominent, or obsolete; pericarp thick; oil-tubes solitary in the intervals or also under the ribs, 2 on the commissural side. Stylopodium short, conic. [Greek, scaly-seed, referring to the rough fruit.]
Four species, natives of the United States. Type species: Daucus divaricatus Walt. Fruit tubercled.
Fruit covered with hooked bristles.
Daucus divaricatus Walt. Fl. Car. 114. 1788.
Leptocaulis divaricatus DC. Mem. Omb. 39. pl. 10. 1829.
Apium divaricatum Wood, Bot. & Fl. 140. 1870.
Very slender and widely branching. Rays of the umbels almost filiform, 1/2'-1 1/2' long, divaricate; flowers about i" broad; pedicels filiform, 3"-6" long; fruit ovate, densely tuberculate, ¥ long, the ribs rather prominent.
Nebraska to Texas, North Carolina and Florida. Also in ballast at Philadelphia. April-May.
Erect, slender, 1°-2° high, divergently branched above. Stem-leaves short-petioled, biternately dissected into narrowly linear or filiform segments; umbels terminal, or axillary, 1/2'-1 1/2' broad; rays 3"-6" long; pedicels 1 1/2"'-2 " long in fruit; fruit ovate, slightly more than ¥' long, more or less tuberculate, usually densely so.
Sandy soil, Indiana to Missouri, Nebraska, Texas and New Mexico. June.
Leptocaulis echinatus Nutt.; DC. Prodr. 4:
107. 1830. S. echinatus Heller, Contr. Herb. F. & M. Coll.
Resembling the preceding species, but lower, seldom over 1° high, the branches ascending or sometimes spreading. Rays of the umbel very slender, 1 1/2 long, or less; fruit about i" long, covered with spreading hooked bristles, the ribs obsolete, the commissure narrow.
Alabama to Missouri, Texas and California. April-May.