Caluptra
Hook-like covering of the capsule of mosses and liverworts, developed from archegonial well.

Calyptrogen
Layer of actively dividing cells formed over apex of growing part of roots in many plants, e.g. grasses; gives rise to root-cap.

Calyx
Outermost part of flowers, consisting usually of green, leaf-like members known as sepals that in the bud stage enclose and protect the other flower parts.

Cambium
A lateral meristem. Layer of actively dividing cells lying between xylem and phloem; forms additional xylem and phloem elements in the process known as secondary thickening. The cambium of a vascular bundle is fascicular cambium; formed from cells of parenchyma between vascular bundles and linking up with fascicular cambium to form a complete ring is interfascicular combium.

Capillary.  A blood vessel formed by the finer division of artery and arterioles.

Capitulum
Kind of inflorescence.

Capsid. (Of virus). Goat of virus particle (vision). Protects enclosed nucleic acid. Is involved in penetration of host cell, aiding attachment to host cell membrane and, in some bacteriophage, providing mechanism for injection of virus nucleic acid into host cell.

Capsomer.  Sub-unit of coat of virus particle (virion).

Capsule. (1) In flowering plants, dry dehiscent fruit developed from a compound ovary (q.v.); opening to liberate seeds in various ways, e.g. by longitudinal splitting from apex to base, the separated parts being known as valves, as in iris; by formation of pores near top of fruit, as in snapdragon; or in the pyxidium, by detachment of a lid following equatorial dehiscence as in scarlet pimpernel. (2) In liverworts and mosses, organ within which spores are formed. (3) In some kinds of bacteria, gelatinous envelope surrounding the cell wall. (4) (Zool). Connective tissue investment of an organ, providing mechanical support.