From The Collaborative International Dictionary of English v.0.48 :
Deergrass \Deer"grass`\, n. (Bot.)
An American genus ({Rhexia) of perennial herbs, with
opposite leaves, and showy flowers (usually bright purple),
with four petals and eight stamens, -- the only genus of the
order Melastomace[ae] inhabiting a temperate clime.
[1913 Webster]