GENERAL KEY TO THE FAMILIES I. SUBKINGDOM PTERIDOPHYTA, FERN PLANTS Plants with typically distinct alternation of generations, the leafy plant (sporophyte) reproducing by non-sexual spores. Spores developing prothallia or flat plates of tissue (gametophyte) bearing antheridia (containing male cells or sperms) and archegonia (containing a female cell or oospore). Oospore ferti- lized in the presence of water by a self-motile sperm. Flowers or seeds none. Ours herbs. Stems not jointed or rush-like. Stems small in comparison with the leaves, often very short, usually un- branched. Land plants, or at least essentially terrestrial; sporangia borne on the lower side or edges of the leaves; spores all of one kind and size (isosporous). Leaf 1, erect in the bud; sporangia borne in spikes, the spikes simple or branched, not green. .OPHIOGLOSSACEAE, p. 25. Leaves several to numerous, circinate in the bud, often large and characteristically much-divided; sporangia borne in clus- ters (sori) on the back or margin of green leaves POLYPODIACEAE, p. 26. Aquatic or subaquatic plants; sporangia and spores of 2 kinds. Sporangia borne in special conceptacles; stems not corm-like. Plants floating in water; leaves minute, entire or 2-lobed. .. SALVINIACEAE, p. 39. Plants rooting in mud; leaves 4-foliolate or filiform MARSILEACEAE, p. 39. Sporangia borne in the leaf-axils; leaves awl-like or linear, clus- tered on a flattened or corm-like stem. .ISOETACEAE, p. 43. Stems more or less elongated, freely branching, closely clothed or imbricated with small awl-like or scale-like leaves; sporangia borne in or near the leaf axils. Spores of one kind LYCOPODIACEAE, p. 41. Spores of two kinds SELAGINELLACEAE, p. 41. Stems jointed or rush-like, hollow, the reduced leaves joined into a toothed sheath at the nodes; sporangia borne on the under side of the scales in a terminal cone-like spike; spores of 1 kind EQUISETACEAE, p. 39. II. SUBKINGDOM SPERMATOPHYTA, SEED PLANTS Plants without distinct alternation of generations, the sexual phase (game- tophyte) much reduced and parasitic upon the sporophyte; egg-cell fertilized through the intervention of the pollen-tube, the developed embryo forming a resting body called a seed. CLASS 1. GYMNOSPERMAE, CONE-BEARING PLANTS Ovules and seeds borne naked on the surface of a scale; stamens and ovules in catkin-like clusters; cotyledons 2 to 17; cone-bearing trees or shrubs, all of ours evergreen; true flowers none; leaves needle-like, narrowly linear, awl-like or scale-like. Trees, rarely shrubs, with resin. Fruit a woody cone (soft and berry-like in Juniperus), containing several to many seeds; ovules in catkins. Cone-scales imbricated, with a conspicuous or minute bract at base on lower side; leaves needle-like or narrowly linear; seeds 2 to each scale, bearing a thin wing PINACEAE, p. 44. Cone-scales without bracts. 21 22 KEY TO THE FAMILIES Leaves narrowly linear and 2-ranked in flat sprays, or lanceolate or awl-like and disposed all around the branchlet; cone-scales not imbricated, ending in broad flattish summits; seeds 2 to 9 to each scale, not winged TAXODIACEAE, p. 54. Leaves minute and scale-like, thickly clothing the ultimate branch- lets; cone-scales imbricated, or with broad flattish sum- mits and not imbricated; seeds 1 to several to each scale, winged or wingless CUPRESSACEAE, p. 55. Fruit berry-like or drupe-like, one-seeded; ovules solitary; leaves narrowly linear, in flat sprays TAXACEAE, p. 59. Shrubs without resin; deserts GNETACEAE, p. 60. CLASS 2. ANGIOSPERMAE, FLOWERING PLANTS Ovules borne in a closed sac or ovary, which becomes the fruit and encloses the seed; cotyledons 1 or 2; plants wirli true flowers, typically with an abbreviated stem (receptacle) bearing regular whorls of perianth parts, stamens, and pistils. SUB-CLASS 1. MONOCOTYLEDONEAE Leaves parallel-veined (except Trillium) ; parts of the flower usually in 3s, rarely in 2s, 4s or 5s; vascular bundles scattered irregularly through the pithy tissue, not in rings or annual layers; embryo with 1 cotyledon; perennial herbs commonly with rootstocks or bulbs, or annuals, or a few trees or shrubs. A. PERIANTH NONE OR CALYX-LIKE WITH SCALE-LIKE DIVISIONS; PARTS OP THE FLOWER MOSTLY UNEQUAL IN NUMBER; CARPELS 1 TO SEVERAL, DISTINCT, OR SOMETIMES UNITED BUT SEPARATING AT MATURITY. 1. Flowers not in the axils of dry chaffy bracts; ovary superior; herbs. Leafless minute aquatics, the stems represented by leaf-like floating fronds LEMNACEAE, p. 194. Leafy plants. Immersed aquatics; leaves filiform or linear, or some floating ones with broad blades; flowers inconspicuous, naked or with a very small calyx, borne on a spike or spadix; stamens 1 to 4; ovaries 1 to 4. NAIADACEAE, p. 63. Plants of marshes or rising out of water. Flowers monoecious; reed-like plants with linear leaves. Inflorescence a dense cylindrical spike. TYPIIACEAE, p. 61. Inflorescence a dense globose head SPARGANIACEAE, p. 62. Flowers perfect, rarely polygamous, in racemes or spikes. Inflorescence with a spathe; calyx none; stamens 6 ARACEAE, p. 193. Inflorescence naked; calyx of 6 (or 3) distinct sepals, or none; stamens 6 or 1 JUNCAGINACEAE, p. 68. 2. Flowers in the axils of dry chaffy bracts, arranged in spikes or spikelets. Stems mostly terete and hollow; leaves in 2 rows; sheaths mostly split open oppo- site the blade; bractlets 2 to each flower; fruit a grain (seed mostly adnate to the pericarp) GRAMINEAE, p. 72. Stems mostly triangular, solid; leaves in 3 rows; sheaths entire; ligule obsolete or minute; bractlet 1 to each flower; fruit an achene (seed free from the pericarp) CYPERACEAE, p. 144. B. PERIANTH ALWAYS PRESENT, ITS SEGMENTS IN 2 SERIES, RARELY IN 1, OFTEN COROLLA-LIKE; PARTS OF THE FLOWER USUALLY EQUAL IN NUMBER; CARPELS UNITED INTO ONE COMPOUND OVARY (EXCEPT ALISMACEAE). Inflorescence without a spathe. Pistil 1. Ovary superior; perianth regular; stamens 6, sometimes 3 or 4. Perianth-segments distinct, green or brown, not petal-like; flowers small or minute; rush-like plants.... JUNCACEAE, p. 196. KEY TO THE FAMILIES 23 Perianth-segments distinct or partly united, at least the inner petal- like; flowers mostly showy; plants not rush-like LILIACEAE, p. 208. Ovary inferior; flowers perfect, mostly conspicuous; perennial. Perianth regular; ovary 3-celled. Stamens 6; leaves (in ours) fleshy, in a basal rosette AMARYLLIDACEAE, p. 252. Stamens 3; leaves 2-ranked, sword-like and sheathing IRIDACEAE, p. 253. Perianth irregular; stamens 1, rarely 2; ovary 1-celled; leave9 sheathing, often reduced to scales. ..ORCHIDACEAE, p. 255. Pistils several, distinct, 1-celled, superior, becoming achenes; perianth of 3 sepals and 3 petals; stamens 6 to many ALISMACEAE, p. 69. Inflorescence with a spathe; pistil 1. Herbs. Ovary inferior; 1 to 3-celled; stamens 3 to 12; aquatic plants; leaves opposite or whorled HYDROCHARITACEAE, p. 72. Ovary superior. Aquatic plants; leaves ribbon-like PONTEDERIACEAE, p. 195. Marsh or bog-perennials; leaves broad ARACEAE, p. 193. Trees; flowers on a spadix or fleshy spike PALMACEAE, p. 193. SUB-CLASS 2. DICOTYLEDONEAE Leaves commonly netted-veined; parts of the flower mostly in 4s or 5s; vascular bundles in a ring around a central pith, the stem, when perennial, increasing in girth by annual layers; embryo with 2 cotyledons; herbs, shrubs or trees. I. APETAXOUS DIVISION. Corolla none; calyx present, herbaceous or often petal-like, sometimes none. A. Flowers monoecious or dioecious, one or both kinds in catkins; trees or shrubs. 1. Leaves opposite. Flowers dioecious. Catkins erect; maritime shrub BATIDACEAE, p. 340. Catkins drooping; montane shrubs GARRYACEAE, p. 731. Flowers monoecious; ovary superior, 2 or 3-celled BDXACEAE, p. 606. 2. Leaves alternate. Both kinds of flowers in catkins. Flowers 1 to each scale or bract; calyx none. Fruit a 1-celled many-seeded capsule; seeds with a coma; flowers dioe- cious; foliage deciduous SALICACEAE, p. 261. Fruit waxy-coated, berry-like; flowers monoecious or dioecious; foliage evergreen or deciduous MYRICACEAE, p. 279. Flowers 2 or 3 to each scale or bract; calyx present; staminate catkins long. pendulous, the pistillate small, spike-like, maturing into a woody cone containing small nutlets BETULACEAE, p. 269. Only the staminate flowers in catkins, the pistillate flowers solitary or clustered, rarely in catkins. Leaves simple. Fruit a nut set in a scaly cup or bur (acorn or chestnut) FAGACEAE, p. 271. Fruit a nut enclosed in a leafy tubular involucre. .CORYLACEAE, p. 270. Leaves pinnately compound; fruit a nut with a fibrous coat JUGLANDACEAE, p. 279. 24 KEY TO THE FAMILIES B. Flowers perfect or unisexual, not in catkins. 1. OVARY SUPERIOR, THAT IS, FREE PROM THE CALYX. a. Flowers hypogynous. * Calyx present; corolla none. Pistil one. Ovary 1-celled; styles or stigmas 1 or more than one. Fruit in dehiscent (circumscissile in some Amaranthaceae). Fruit dry (an achene or utricle) ; stamens 1 to 9. Herbage with stinging hairs; flowers very small, monoecious, in a catkin-like inflorescence; sepals 4; stamens 4; herbs URTICACEAE, p. 280. Herbage without stinging hairs. Plants commonly scurfy, of alkaline or maritime habitat; sepals herbaceous, or in unisexual flowers, tha pistillate without calyx and enclosed by 2 bracts; bractlets none; stamens 1 to 5; leaves alternate, rarely opposite or leafless; stipules none CHENOPODIACEAE, p. 319. Plants not scurfy. Calyx not tubular; leaves alternate or opposite or basal. Fruit a triangular or lenticular achene; calyx colored or herbaceous. 5 or 6-cleft or -parted; flowers with or without bract- lets ; stamens 3 to 9; stipules present or none POLYGONACEAE, p. 286. Fruit a utricle; calyx scarious, 5 or 3-cleft or -parted; flowers with bractlets; stamens 3 to 5 (rarely 1); stipules none AMARANTHACEAE, p. 333. Calyx tubular, corolla-like, the base of the tube hard- ening and enclosing the achene; stamens 3 to 5; leaves opposite, without stipules NYCTAGINACEAE, p.