4. Enantioblastæ. These ought perhaps to be amalgamated with the following family.
5. Liliifloræ. These advance from forms with the typical diagram and hypogynous flower, to epigynous and reduced forms.
6. Scitamineæ and
7. Gynandræ. Two isolated families, which probably have taken their origin from Liliifloræ, and have epigynous, mostly zygomorphic, and much reduced forms.
Family 1. Helobieæ.
To this family belong only water- or marsh-plants; the endosperm is wanting, and they possess an embryo with a very large hypocotyl prolonged downwards and often club-like. The perianth is often differentiated into calyx and corolla; the flower is regular, and in the first orders to be considered, may be reduced to the ordinary Monocotyledonous type; there are, however, usually found two 3-merous whorls of carpels (Fig. [282]), and thus in all 6 whorls, or again, the number of carpels may be indefinite; the number of stamens also may be increased, either by the division of the members of a whorl, or by the development of additional whorls. Syncarps,[26] with nut or follicular fruitlets, are very common, for example, in the first orders; in the last (Hydrocharitaceæ) the carpels are not only united, but the ovary is even inferior.
The primitive type appears to be a hypogynous flower, similar to that of the Juncaginaceæ or Alismaceæ, with several 3-merous whorls, and free carpels, each with many ovules; the green perianth in this instance being no doubt older than the coloured ones. If we take a flower with this structure as the starting point, then the family developes partly into epigynous forms, partly into others which are so strongly reduced and exceptional that it is scarcely possible to refer them to the ordinary type. The family, through the peculiar Zostereæ, appears to approach the Araceæ, in which Potamogetonaceæ and Najadaceæ are included by some authorities. However, the inclusion of Potamogeton, and with it Ruppia and Zannichellia, in the Juncaginaceæ appears quite correct. It would scarcely be right to separate Zostereæ from these. Great stress has often been laid upon the similarity with the Ranunculaceæ which is found in the Alismaceæ, but it is scarcely more than an analogous resemblance.
Order 1. Juncaginaceæ. The ☿, regular, hypogynous flowers have the perianth 3 + 3, sepaloid, stamens 3 + 3 (with extrorse anthers), and carpels 3 + 3 (free or united), of which last, however, one whorl may be suppressed (in Triglochin maritima all 6 carpels are developed, in T. palustris the inner whorl is unfertile). Inflorescence long spikes. Embryo straight.—Marsh-plants with radical, rush-like leaves, arranged in two rows, and often sheathing and ligulate (“squamulæ intravaginales”); the inflorescence is a spike or raceme.—Scheuchzeria. Carpels almost free; in each at least two ovules. Follicles.—Triglochin has long, fine racemes without bracts or bracteoles; one ovule in each carpel. The carpels in the two native species are united, but separate when ripe as a schizocarp, loosening from below; they open along the ventral suture or remain closed; a linear central column remains. The most reduced is Lilæa (1–2 sp. Am.)—Protogynous. About 10 species. Temp. Fossils in Tertiary.
Order 2. Potamogetonaceæ. The aquatic plants belonging to this order are perennial, living entirely submerged, or with floating leaves, and preferring still water. The leaves are alternate, in some linear and grass-like, in others there is an elliptical floating blade, supported by a linear submerged petiole. Axillary scales. The fruit is generally a syncarp with nuts or drupes; the embryo is curved, of very various forms.
Potamogeton (Pond-weed). The rhizome is creeping, sympodial (with two internodes in each shoot-generation); the inflorescence is a terminal, many-flowered spike, without floral-leaves; below it are found 2 foliage-leaves placed nearly at the same height, from whose axils the branching is continued cymosely. The flowers are ☿, 4-merous, naked, and consist only of 4 stamens, with the connectives, broadly developed at the back of the anthers, resembling a perianth, and of 4 free, sessile carpels. They are common plants in fresh water. The spike, during the flowering, is raised above the water. Wind-pollinated and protogynous.—Closely allied is Ruppia (Tassel Pond-weed), in salt or brackish water. The spike has only two naked flowers, each consisting of 2 stamens and 4 carpels. The stalks of the individual carpels are considerably prolonged.—Zannichellia (Horned Pond-weed) is monœcious; the ♀-flower consists of 4 (2–9) carpels, with membranous, bell-shaped perianth; long styles; the ♂-flower has 1 (-2) stamens. Althenia.