June Lockhart, the soft-spoken actress who exuded earnest maternal wisdom and wistful contentment in two very different mid-20th-century television roles, on the heartwarming children’s series “Lassie” and the futuristic “Lost in Space,” died Thursday at her home in Santa Monica, California. She was 100.

Her death was announced by a spokesperson, Harlan Boll.

Lockhart replaced Cloris Leachman in the role of Ruth Martin, a farm wife and the foster mother of Jon Provost’s character and his courageous collie, Lassie, in 1958, at the beginning of the show’s fifth season. After six years of dispensing homespun wisdom, Lockhart was herself replaced, along with her human co-stars, in favor of a forest-ranger character (Robert Bray) who would guide the show’s canine heroine through her further a

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