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.
Out of nearly 100 species only a few are grown in any quantity - the most popular being the South African A. variegata, the well-known "partridge-breasted" Aloe. The stout leaves 6-8 in. long are deep green spotted with grey and edged and keeled with white. It is easily grown in loam and mortar rubble in a greenhouse, and is increased by offsets from the base.