Theca vs Thecal - What's the difference?

As a noun theca

is (biology) any external case or sheath.

of or pertaining to a theca.

(en-noun)

(biology) Any external case or sheath.

(botany) The pollen producing organ usually found in pairs and forming an anther.

(medicine) The twin layers of cells surrounding the basal lamina of an ovarian follicle

(microbiology, planktology) The membrane complex enveloping the cells of certain plankton including diatoms and dinoflagellates

(coral science) The calcareous wall of a corallite, the exoskeleton of a coral polyp

{{der3, thecal , thecate , thecoma , epitheca , ootheca , gnathotheca , hypotheca , spermatheca , theca externa , theca interna , theca folliculi}}

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(-)

Of or pertaining to a theca.

Possessing a theca.

The latter has the sporophyte seta 4 cells in diam. and has thecal Lejeunea -type androecial branches