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..
Sepals very unequal, the two lateral ones large and petaloid. Petals 3, united into a tube which is split on the back, and more or less adnate to the stamens. Stamens 8 or 6, monadelphous below, or diadelphous; capsule membranous, compressed, dehiscent along the margin.
Seeds 1 in each cavity, generally hairy. [Greek, much milk.]
A genus of about 450 species, of wide geographic distribution. Besides the following, about 40 others occur in the southern and western parts of North America. Type species: Polygala vulgaris L.
* Flowers in corymbed spike-like racemes at the summit of the stem, yellow.
Basal leaves long, narrow, acuminate.
Basal leaves spatulate, or obovate.
** Flowers in solitary spikes or spike-like racemes, terminating the stem and branches.
Basal leaves spatulate, or obovate; flowers orange yellow.
Basal leaves inconspicuous, or wanting; flowers not yellow.
Spikes sessile, or nearly so; wings deltoid.
Spikes peduncled; wings lanceolate-ovate.
Leaves verticillate and alternate; spikes 2" - 3" thick, acute.
Alternate leaves predominating; spikes loose, long; flowers more purple.
Leaves all alternate.
Petals united into a cleft tube, 3"-4" long; flowers pink.
Petals not conspicuously united into a tube.
Spikes ovoid to globose.
Bracts persistent; flowers rose-purple to white.
Spikes blunt; wings broadly ovate.
Spikes acutish; wings narrowly ovate or elliptic.
Bracts deciduous; flowers rose-purple.
Leaves oblanceolate to linear, 2"-6" long; flowers greenish to purplish.
Leaves lanceolate, 1' - 2' long; flowers white or greenish.
Spikes elongated-conic; flowers white.
*** Flowers distinctly racemose, rose or purple.
**** Flowers 1-4, large, axillary, but apparently terminal, rose-purple to white.