• Webster's Revised Unabridged Dictionary
    • n Heterocyst (Bot) A cell larger than the others, and of different appearance, occurring in certain algæ related to nostoc.
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Century Dictionary and Cyclopedia
    • n heterocyst In botany, one of a class of abnormal cells found in algæ of the order Nostocaceæ. In the genus Nostoc, which may be taken as the type, the plants consist of rounded cells, loosely joined together in filaments, and usually embedded in a glutinous jelly. At irregular intervals in the filaments certain larger clear cells, the heterocysts, are produced. These heterocysts have differently colored watery cell-contents, and seem incapable of further development. They are probably connected in some way with reproduction, but their real nature is unknown. According to Farlow (“Marine Algæ of New England,” p. 180), the term has been wrongly applied to certain of the basal cells of some of the species of Melobesia, the organs not being homologous.
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Webster's Revised Unabridged Dictionary
Hetero-, + cyst,