This section is from the book "Nature's Garden", by Neltje Blanchan. Also available from Amazon: Nature's Garden; An Aid To Knowledge Of Our Wild Flowers And Their Insect Visitors.
Flowers - White or pale greenish yellow, about 1/2 in. across, loosely scattered in small clusters on slender peduncles. Calyx persistent, 5-cleft, with little bracts between the re-flexed divisions; 5 petals, equalling or shorter than the sepals; stamens and carpels numerous, the latter collected on a short, bristly-hairy receptacle; styles smooth below, hairy above, jointed. Stem: 2 1/2. ft. high or less, slender, branching above. Leaves: Seated on stem or short petioled, of 3 to 5 divisions, or lobed, toothed; small stipules; also irregularly divided large root-leaves on long petioles, 3-foliate, usually the terminal leaflet large, broadly ovate; side leaflets much smaller, all more or less lobed and toothed. Fruit: A ball of achenes, each ending in an elongated, hooked style.
Preferred Habitat - Woodland borders, shady thickets and roadsides.
Flowering Season - June - September.
Distribution - Nova Scotia to Georgia, west to the Mississippi or beyond.
Small bees and flies, attracted to sheltered, shady places by these loosely scattered flowers at the ends of zig-zagged stems, pay for the nectar they sip from the disk where the stamens are inserted, by carrying some of the pollen lunch on their heads from the older to the younger flowers, which mature stigmas first. But saucy bumblebees, undutiful pilferers from the purple avens, rarely visit blossoms so inconspicuous. Insects failing these, they are well adapted to pollenize themselves. Most of us are all too familiar with the seeds, clinging by barbed styles to any garment passing their way, in the hope that their stolen ride will eventually land them in good colonizing ground. Whoever spends an hour patiently picking off the various seed tramps from his clothes after a walk through the woods and fields in autumn, realizes that the by hook or by crook method of scattering offspring is one of Nature's favorites. Simpler plants than those with hooked achenia produce enormous numbers of spores so light and tiny that the wind and rain distribute them wholesale.