Azollaceae

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GENUS (1) Azolla., is divided into six species.

THE AZOLLACEAE are commonly grouped within the Salviniaceae. Floating aquatics, members of the family are characterized by the most complex reproductive structures of any known plant.

SORI are short-stalked, and borne on the lower of the two leaf lobes.

SPORANGIA are enclosed in an indusium, and bear either one megaspore or several microspores.

SPORES are trilete, and heterosporous. The megaspore has an accessory structure, the columella, which bears floats. The microspores are embedded in massulae, which have projecting structures called glochidia on their outer surface.

STEMS are short, creeping, and slender. Usually bearing short roots, they are indurated, and sometimes also have trichomes.

LEAVES are bilobed, and between 0.5-1.5 cm long. The upper lobe is usually palpillate, without veins. Leaves in Anabaena are characterized by a basal cavity in which a blue-green alga (i.e. Cyanobacterium) grows. Anabaena is also able to fix its own nitrogen.

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Azolla