polypodiaceae: ferns: a large family that in some classification systems has been subdivided into several families (including Aspleniaceae and Blechnaceae and Davalliaceae and Dennstaedtiaceae and Dryopteridaceae and Oleandraceae and Pteridaceae)
fern family: families of ferns and fern allies
rayleigh disk: an acoustic radiometer consisting of a light disk suspended from a quartz thread; when exposed to a progressive sound wave its torque can measure velocity