Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
inter-spersus, a, um [spargo], strewn, sprinkled upon or between, interspersed (post-class.): interspersus rara canitie, App. M. 5, p. 165, 36: sunt multa naturae munere interspersa, id. Mag. p. 299, 30.