85. LEMNACEÆ.--Minute floating plants, with green, cellular fronds, rarely flowering. Flowers very small, enclosed in a bract. Stamen 1. Ovary one-celled. Ovules 1 to 7. (The Duckweed Family.) 86. ARACEÆ.--Herbs with net-veined, radical leaves; and small flowers on a fleshy spadix enclosed in a leafy sheath. Perianth of 6 parts, or absent. Stamens 1 to 6. Ovary of one to three cells. Fruit berry-like. (The Cuckoo Pint Family.) 87. TYPHACEÆ.--Erect marsh plants, with long, narrow leaves; and small monoecious flowers in conspicuous spikes or heads. Perianth absent. Stamens many. Fruit a one-seeded drupe. (The Reed-mace Family.) 88. JUNCACEÆ.--Rush-like herbs, with cylindrical or narrow leaves, and small, brown flowers. Perianth membranous, of 6 parts. Stamens 6. Carpels 3. Fruit a 3-valved capsule. (The Rush Family.) * * * * * 89. CYPERACEÆ.--Grassy herbs, with usually solid, triangular stems; and linear leaves, with tubular sheaths. Flowers in spikelets, unisexual or perfect. Stamens 1 to 3. Carpels and stigmas 2 or 3. (The Sedge Family.) 90. GRAMINEÆ.--Grassy herbs, with hollow stems; and linear leaves, with split sheaths. Flowers usually perfect. Stamens usually 3. Stigmas 1 or 2. (The Grass Family.) II THE POLLINATION AND FERTILISATION OF FLOWERS Since flowers are the reproductive organs of the plant it seems only natural to suppose that the wonderful variety of colour and form which they exhibit might have some connexion with the processes concerned in the propagation of their respective species, and the more we study the nature of the flowers and observe the methods by which pollen is transferred from stamens to stigmas, the stronger becomes our conviction that the diversities mentioned are all more or less connected with the one great function of reproduction. This being the case, we propose to devote a short chapter to a simple account of the uses of the parts of a flower, and to the various contrivances on the part of the plant to secure the surest and best means of perpetuating the species. It has already been stated that the stamens produce pollen cells, and that the ovary contains one or more ovules. As soon as the anthers are mature, they open and set free the pollen cells they contained. A stigma is said to be mature when it exposes a sticky surface to which pollen cells may adhere, and on which these cells will grow. When a pollen cell has been transferred to such a stigma, it is nourished by the fluid secreted by the latter, and sends out a slender, hollow filament (the pollen tube) which immediately begins to descend through the stigma, and through the style, if any, till it reaches the ovary. [Illustration: POLLEN CELLS THROWING OUT THEIR TUBES]