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.
Three small-flowered, white, purple-veined, and almost beardless species which prefer to dwell in moist meadows, damp, mossy places, and along the borders of streams, are the Lance-leaved Violet (V. lanceolata), the Primrose-leaved Violet (V primulaefolia), and the Sweet White Violet (V. blanda), whose leaves show successive gradations from the narrow, tapering, smooth, long-petioled blades of the first to the oval form of the second and the almost circular, cordate leaf of the delicately fragrant, little white blanda, the dearest violet of all. Inasmuch as these are short-spurred species, requiring no effort for bees to drain their nectaries, no footholds in the form of beards on the side petals are provided for them. The purple veinings show the stupidest visitor the path to the sweets. (See pp. 29-31.)
The sprightly Canada Violet (V. Canadensis), widely distributed in woodlands, chiefly in hilly and mountainous regions, rears tall, leafy stems terminated by faintly fragrant white or pale lavender blossoms, purple-tinged without and purple-veined, the side petals bearded, the long sepals tapering to sharp points. Here we see a violet in the process of changing from the white ancestral type to the purple color which Sir John Lubbock, among other scientists, considers the highest step in chromatic evolution. This species has heart-shaped, saw-edged leaves which taper acutely. From May even to July is its regular blooming season; but the delightful family eccentricity of flowering again in autumn appears to be a confirmed habit with the Canada violet.
Sweet White Violet (Viola blanda)
Lance-Leaved Violet (Viola lanceolata)