filament; protonema; trichome
Biological term for a thread-like structure, especially in plants, algae, or fungi. Protonema is the early filamentous stage of mosses; trichome refers to hair-like outgrowths on plants.
The protonema of mosses is the first structure formed after spore germination.
Trichomes on the leaf surface protect the plant from drying out.
mitochondria
Rare or obsolete synonym for ミトコンドリア. The cross-reference suggests this usage is not standard; modern biology uses ミトコンドリア.
See also: ミトコンドリア
In older literature, 糸状体 can refer to mitochondria.
Compound of 糸状 (thread-like) and 体 (body/structure). The reading しじょうたい follows standard on'yomi. The mitochondria sense likely arose from early microscopic observations describing them as thread-like bodies.