KEY TO THE ORDERS AND FAMILIES DESCRIBED IN VOLUME I Phylum PTERIDOPHYTA 1 Plants not producing true flowers and seeds; the embryo not formixc. a RESTING stage WITHIN THE SPORANGIUM. Plants with broad fern-like leaves ; spores all alike. Gametophyte subterranean, yellowish and without chlorophyll ; vernation straight or inclined. Order 1. Ophioglossales. Only one family. Fam. 1. Ophioglossaccae. 1 Gametophvte terrestrial, green; vernation circinnate. Order 2. Filicales. Only one family. ' Fam. 2. Polypodiaceae. 5 Plants not fern-like, the leaves various; spores of two kinds (except m the Lycopodiaceae), those producing the female gametophytes larger (megaspores). Spores produced in usually thick-walled sporocarps on peduncles. Order 3. Salviniales. Plants rooting in the mud ; leaves filiform or 4-f oliolate. Fam. 3. Marsileaceae. 33 Plants small, floating aquatics ; leaves scale-like, 2-ranked on the branched stems. Fam. 4. Salviniaceae. 35 Spores produced in sporangia either in terminal cone-like clusters or in the axils of the leaves. Plants with tubular elongated leaves, borne on a short corm-like caudex ; sporangia borne in the axil of the leaves. Order 4. Isoetales. Only one family. Fam. 5. Isoctaceae. 35 Plants rush-like or moss-like; with evident simple or branching stems. Stems jointed, rush-like; sporangia borne in terminal cone-like clusters. Order 5. Equisetales. Only one family. Fam. 6. Equisetaceac. 38 Stems usually branched, clothed with the small scale-like leaves ; sporangia in the axils of the leaves. Order Lycopodiales. Spores all of one sort and size. Fam. 7. Lycopodiaceae. 43 Spores of two sizes (microspores and megaspores). Fam. 8. ScIagineUaceae. 46 Phylum SPERMATOPHYTA 50 Plants producing true flowers and seeds; the embryo forming a resting STAGE within THE MEGASPORANGIUM (SEED). Ovules borne on the surface of a scale (sporophyll), or this sometimes apparently wanting; stigmas none. Class 1. Gymnospennac. Ovules borne within an inclosed cavity (ovary) formed by one or more united sporophylls ; stigmas present. Class 2. Angiospcrmae. Class 1. GYMNOSPERMAE 50 Perianth none; trees or shrubs with needle-like or scale-like leaves not sheathing. Fruit a single stone, enclosed or subtended by a fleshy integument. Order 1. Taxales. Only one family represented. Fam. 1. Taxaccac. 50 Fruit a cone with several ovule-bearing woody scales (coalescent and berry-like in Juniperus and Sabina). Order 2. Pinales. Leaves and floral parts spirally arranged. Buds scaly; leaves jointed at base, ultimately deciduous; pollen sacs and ovules 2 to each scale. Fam. 2. Pinaccae. 52 Buds naked ; leaves decurrent and persistent on the ultimately deciduous branchlets ; pollen sacs and ovules several to each scale. Fam. 3. Taxodiaceae. 68 Leaves and floral parts arranged in cycles of 2 or 3. Fam. 4. Cuprcssaccae. 70 Perianth present, urn-shaped; ours horsetail-like desert shrubs with sheathing scale-like leaves. Order 3. Gnetales. Represented by one family. Fam. 5. Ephedraceae. 77 ix
