Larkspur

Description:
Very thin, dark green, alternate leaves,  round but deeply cut like fingers on a hand with a long leaf stalk, about 2 inches across, or in other varieties larger, less cut, more complete but deeply lobed.   Larger and more leaves toward bottom, fewer and more fine upward on stem. 
One to several hollow stems rise from robust roots, stems may be fuzzy.
Many non symmetrical 5 petal flowers on upper stem are purple to blue with protruding chin and a distinct backward pointing spur.  Each flower develops into several long narrow seed pods; joined, brown, sack like and open at the top, about ¾ inch deep, filled with many tiny dark seeds. 
All parts of the larkspur plant are toxic with seeds being the most poisonous.  Horses do not usually eat a harmful amount, sheep are little affected, cattle are the main victims of fatal poisoning.  The plant contains alkaloids such as delphinine and ajacine, which affect the nervous system causing respiratory paralysis then death (wikipedia).  After crushing, Native Americans rubbed their hair with the plant as lice control.