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Manual of the New Zealand Flora.

Order XCV. SalviniaceÆ

Order XCV. SalviniaceÆ.

Fugacious annuals, of small size, floating in quiet waters. Stems simple or branched. Leaves small, often minute, apparently distichous, sessile or shortly petiolate, simple or lobed. Sporocarps or conceptacles on the under-surface of the stem, either clustered page 1031on the divisions of an altered submerged leaf, or in pairs in the axils of the leaves, globose or ovoid, membranous, indehiscent, of two kinds, both borne on the same plant; one kind containing a single or many macrosporangia, the other enclosing numerous microsporangia. Macrosporangia containing a single macrospore; microsporangia with numerous microspores.

Genera 2; species about 18, mainly tropical or subtropical. In germination the macrospore produces a rather large prothallium, which remains attached to it, and which bears one or more archegonia. The microspores each develop a rudimentary prothallium bearing a single antheridium containing spermatozoids, fertilisation taking place in the same way as in ferns. In the genus Salvinia, which is not found in New Zealand, the antheridia are formed while the microspores are contained within the microsporangium; but in Azolla the microspores escape in groups called massulæ, each with its proper membrane, and the antheridia are developed within the massulse.