No chatf-like bracts. Stigmas 2................ 184

Oleaceae.- Trees. Leaves pinnately compound. Fruit a 1seeded samara............................... 181

Urticaceae. - Trees. Leaves simple. Fruit a 1-seeded samara winged all round, or a drupe.............. 198

Lauraceae; - Trees or shrubs. Flowers dioecious. Sepals 6, petal-like. Stamens 9, opening by uplifting valves. 193

Thymeleaceae. - Shrubs with leather-like bark, and jointed branchlets. Flowers perfect, preceding the leaves. Style thread-like............................. 194

B. Flowers In catkins.

* Sterile or staminate flowers only in catkins.

Juglandaceae. - Trees with pinnate leaves. Fruit a nut with a husk.................................. 202

Cupuliferae. - Trees with simple leaves. Fruit one or more nuts surrounded by an involucre which forms a scaly cup or bur........................ 204

* * Both sterile or fertile flowers in catkins, or catkin-like heads.

Salicaceae. - Shrubs or low tree3. Ovary 1-celled, many-seeded ; seeds tufted with down at one end...... 209

Platanaceae. - Large trees. Stipules sheathing the branch-lets. The flowers in heads... ................. 201

Myricaceae. - Shrubs with resinous-dotted, usually fragrant, leaves. Fertile flowers one under each scale. Nutlets usually coated with waxy grains.. 203

Betulaceae. - Trees or shrubs. Fertile flowers 2 or 3 under each scale of the catkin. Stigmas 2, long and slender................ .................... 207

Ovules and seeds naked, on the inner face of an open scale; or, in Taxus, without any scale, but surrounded by a ring-like disk which becomes red and berry-like in fruit.

Coniferae. - Trees or. shrubs, with resinous juice, and mostly awl-shaped or needle-shaped leaves. Fruit a cone, or occasionally berry-like.............. 214

Distinguished ordinarily by having straight-veined leaves (though occasionally net-veined ones), and the parts of the flowers in threes, never in fives. Wood never forming rings, but interspersed in separate bundles throughout the stem. Cotyledon only 1.

Flowers collected on a spadix, with or without a spathe or sheathing bract. Leaves sometimes net-veined.

Abaceae. - Herbs (either flag-like marsh-plants, or terrestrial, ) with pungent juice, and simple or compound leaves, these sometimes net-veined. Spadix usually (but not always) accompanied by a spathe. Flowers either without a perianth of any kind, or with 4-6 sepals............................ 217

Typhaceae. - Aquatic or marsh plants, with linear straight-veined leaves erect or floating, and monoecious flowers. Heads of flowers cylindrical or globular, no spathe, and no floral envelopes............. 219

Lemnaceae. - Small aquatics, freely floating about..... 218

Naiadaceae. - Immersed aquatics. Stems branching and leafy. Flowers perfect, in spikes, generally on the surface....................................... 221

Flowers not collected on a spadix, furnished with a corollalike, or occasionally herbaceous, perianth.

A. Perianth superior (adherent to the ovary).

* Flowers dioecious or polygamous, regular.

Hydrocharidaceae. - Aquatics. Pistillate flowers only above water; perianth of 6 pieces.............. 226

Dioscoreaceae. - Twiners, from knotted rootstocks. Leaves heart-shaped, net-veined. Pod with 3 large wings. 236

* * Flowers perfect.

Orchidaceae. - Stamens 1 or 2, gynandrous. Flowers irregular ........................................ 226

Iridaceae.- Stamens 3..................... ......... 235

Amaryllidaceae. - Stamens 6. Flowers on a scape from a bulb___.................................... 236

B. Perianth Inferior (free from the ovary).

Alismaceae. - Pistil apocarpous : carpels in a ring or head, leaves with distinct petiole and blade........... 224

Smilaceae. - Climbing plants, with alternate ribbed and net-veined petioled leaves. Flowers dioecious... 237

Trigloehin, in Alismaceae. - Rush-like marsh herbs. Flowers in a spike or raceme. Carpels when ripe splitting away from a persistent axis........................ 224

LiliaceAE. - Perianth of similar divisions or lobes, mostly 6, but in one case 4. One stamen in front of each division, the stamens similar................... 237

Trillium, in Liliaceae. - Perianth of 3 green sepals and three coloured petals........................................ 237

Pontederiaceae. - Stamens 6, 3 long and 3 short. Perianth (blue or yellow) tubular, of 6 lobes. Aquatics.. 247

Juncaceae. - Perianth wholly glumaceous, of similar pieces. 243 Xyridaceae. - Perianth partly glumaceous; inner set of 3 yellow petals. Flowers in dense heads, perfect. 247 Eriocaulonaceae. - In shallow water. Flowers monoecious or dioecious, in a small woolly head, at the summit of a 7-angled scape. Leaves in a tuft at the base........................................ 247

Flowers without a true perianth, but subtended by thin scales called glumes.

Cyperaceae. - Sheaths of the leaves not split............ 248

Gramineae. - Sheaths of the leaves split on the side away from the blade................................ 251

Plants without stamens and pistils, reproducing themselves by spores instead of seeds.

Stem containing vascular as well as cellular tissue.

Filices. - Spores produced on the fronds............... 257

Equisetaceae- Spores produced on the under side of the shield-shaped scales of a terminal spike or cone. 267

Lycopodiaceae. - Low, long-stemmed, moss-like evergreens. Spores-cases produced in the axils of the simple leaves or bracts. Spores of one kind only....................................... . 269

Selaginellaceae. - Spores of two kinds, large and small. Spore-cases solitary in the axils of small 4-ranked leaves, or at the bases of linear radical leaves.... 270

Salviniaceae. - Sporocarps beneath the stem. Floating aquatics, pinnately branched, with minute imbricated leaves.................................. 271