Mare's-tail

n.	1.	A long streaky cloud, spreading out like a horse's tail, and believed to indicate rain; a cirrus cloud. See Cloud. Mackerel sky and mare's-tails Make tall ships carry low sails. - Old Rhyme.
	2.	(Bot.) An aquatic plant of the genus Hippuris (Hippuris vulgaris), having narrow leaves in whorls.