This occurs in northeastern woodlands on base-rich soils, with records as far south as c. Ill. and c. Ind. (K); but the records from s. Ill. (ML) do not appear to be verified (SERNEC). C. cephaloidea is close to sparganioides, but differs in its more condensed mature spikes (with lower internodes ca. 0.5-1 cm versus 2-3 cm), and in other obscure features (F, FNA 23); 2n = 50 (versus 46, 48). Ky. records remain uncertain. There is a verified coll. by C.E. Mueller, now at MO ("ex herb Arthur D. Pease, Wilson, New York"); but it is labeled just "Louisville, Ky. 1889" and that provenance may be doubted. There have also been unverified reports, including various synonyms, from WARR (Pr in addenda), perhaps FAYE (Short & Peter 1835; Anderson 1924), and elsewhere. However, the coll. named C. muricata L. var. cephaloidea Dewey by C.W. Short at PH was det. by K. Mackenzie as C. laevivaginata.