This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
These are easily grown Composites with Ageratum-like flowers, white or reddish purple. They are raised from cuttings in spring, and require greenhouse treatment in winter. The best kinds are atrorubens, riparium, trapezoideum, etc.