Isoetes japonica ("Mizunira")

Japanese name: ミズニラ （水韮）
Scientific name: Isoetes japonica

[Overview]
A summergreen aquatic fern growing in ponds, small streams, wetlands and similar places.
It is a perennial where it is flooded throughout the year, and an annual where it dries up.
Underground there is a tuber 5 cm long and 2–3 cm across.
The tuber is shallowly divided into 3 parts and is blackish brown.
The leaves grow in clusters from the top of the rootstock; they are slightly angular, cylindrical, 2–7 mm wide, bright green and soft.
In places without flowing water, such as wetlands, the leaves stand upright, while in running water they stream downstream, and the longest reach 1 m in length.
The leaf base is whitish and ovate, and bears sporangia in a hollow.
Mizunira is heterosporous, having female white megaspores and male pale brown microspores; the former are borne at the base of the megasporophylls and the latter at the base of the microsporophylls of the same plant.
The surface of the megaspores is honeycomb-like.

[Cultivation]
It is easy to grow in a shallow water-filled dish or similar container.
Cultivation in an aquarium is also relatively easy; it can be grown at water temperatures of 20–28 °C and adapts even to high temperatures of 27–28 °C.
It grows well when given bright lighting, planted in a nutrient-rich substrate, and supplied with added carbon dioxide.

[Notes]
The name comes from the fact that it grows in wet places and looks like nira (garlic chives).

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