1911 Encyclopædia Britannica/Compass Plant

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COMPASS PLANT, a plant of the North American prairies, which takes its name from the position assumed by the leaves. These leaves turn their edges to north and south, thus avoiding the excessive mid-day heat, while getting the full benefit of the morning and evening rays. The plant is known botanically as Silphium laciniatum, and belongs to the natural order Compositae. Another member of the same order, Lactuca Scariola, which has been regarded as the origin of the cultivated lettuce (L. sativa), behaves in the same way when growing in dry exposed places; it is a native of Europe and northern Asia which has got introduced to North America.