Lygodium japonicum var. japonicum (Japanese climbing fern, "Kanikusa")

Japanese name: カニクサ （蟹草）
Scientific name: Lygodium japonicum var. japonicum

[Overview]
A fern found at woodland edges, roadsides, stone walls and similar places near human settlements.
In Japan it is summergreen, but in warm regions without frost it is evergreen.
In regions with rainy and dry seasons, it dies back in the dry season.
It looks like a vine, but it is actually a single long leaf.
What looks like the stem is the rachis of the leaf, which twines around other plants and grows 2–3 m long.
The rhizome creeps and is covered with blackish brown hairs.
One leaf emerges from the rhizome, with a leaf stalk 30 cm long.
The base of the leaf stalk bears blackish brown hairs.
On the long, extending rachis, pinnae each made up of a pair of pinnules are borne at intervals of 10–20 cm.
The pinnae are twice pinnately divided.
The upper pinnae are divided even more finely, become spore-bearing leaves, and bear sporangia along their margins.

[Uses]
The spores are called kaikinsha and are used as a crude drug.
The vine is used as a material for weaving kago (baskets).

[Notes]
The Japanese name is said to come from children using this vine to fish for crabs.

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