Section of Span-Roofed Pit Small 320×235 Medium 640×470 Large 1024×751 Download TIFF Original 2400×1761 | (813.4 KB) Description A diagram consisting of a section of a span-roofed pit. These pits are useful for plant culture. A, Ordinary Soil; b, Passage; c, Heated Chambers; d, Plunging Beds; e, Hot-Water Pipes. Keywords culture, plant, plant culture, span, span roofed, span roofed pit, span-roofed, span-roofed pit, tree Galleries Greenhouses and Cold Frames Source: Nicholson, George The Illustrated Dictionary of Gardening, Div. VI (London, England: L. Upcott Gill, 1884)