nostoc
A genus of cyanobacteria that forms gelatinous colonies, often found in damp soil or freshwater. In Japanese, it is commonly referred to by its katakana name.
Some species of nostoc are edible.
Katakana spelling is standard for this organism name.
Kanji spelling is rare; the word is usually written in kana.
The kanji 念珠藻 literally means 'rosary algae', referring to the bead-like appearance of the colonies. The reading is a direct on'yomi of the kanji.