KEY TO THE FAMILIES. 



A. Plants without flowers ; reproduction by spores Division 1 Pteridophyta. 



A. Plants with flowers ; reproduction by pollen and ovules, 



the latter ripening into seeds Division 2 Spermatophyta. 



B. Seeds naked, i.e., not enclosed in an ovary ; no perianth 



Subdivision 1 Gymnosperms. 



B. Seeds enclosed in an ovary ; perianth usually present 



Subdivision 2 Angiosperms. 



C. Embryo with 1 cotyledon ; leaves usually with 

 parallel nerves ; perianth frequently of 2 whorls of 

 3 parts each, but sometimes absent Class 1 Monocotyledons. 



C. Embryo with 2 cotyledons ; nerves of the leaves 

 branching pinnately and often reticulate ; perianth 

 usually in 1 or 2 whorls of 4 to 5 parts each Class 2 Dicotyledons. 



Petals, when present, usually free ; perianth simple 



and petaloid or herbaceous, or divided into calyx 



and corolla, or sometimes absent Subclass 1 Archichlamydeae. 



Petals usually united into a corolla ; perianth always 



double, but calyx sometimes inconspicuous 



Subclass 2 Metachlamydeae. 



DIVISION 1.— PTERIDOPHYTA (Vascular Cryptogams). 



A. Class F1LICALES (Fernlike Plants). Leaves large, usually 

 divided or pinnatisect, with small spore -cases in clusters 

 on the undersurface. 



B. Spores of one kind. 



C. Spore -cases with a ring. 



Spore-cases with a complete oblique ring ; tree-ferns Cyatheaceae 1. 

 Spore cases with an incomplete longitudinal ring, and 



with or without indusium Polypodiaceae 2. 



Spore -cases few, with a transverse ring and opening 



by a longitudinal slit ; no indusium Gleicheniaceae 3. 



Spore -cases sessile in 2 rows, with a complete ring at 

 the summit and a longitudinal slit ; no indusium. . . Schizaeaceae 4. 

 C. Spore-cases without a ring ; no indusium. 



Spore -cases clustered, stalked, with a longitudinal 



slit ; trunk thick Osmundaceae 5. 



Spore-cases in 2 rows along the spike like fertile leaf, 



and opening in a longitudinal slit Ophioglossaceae 6. 



B. Spores of 2 kinds, producing male and female prothalli. 



Spore-cases containing both sexes within 2 fertile leaves 



united in the form of a capsule ; barren leaf usually 



of 4 leaflets (Nardoo) Marsiliaceae 7. 



Spore-cases of 1 sex only, within the fruiting leaves ; 



small water-plants Salviniaceae 8. 



A Class LYCOPODIALES (Plants like Clnbmoss). Leaves 

 small, undivided ; spore -cases solitary, sessile in the 

 axils of the leaves. 



D. Spores of one kind ; moss-like plants with small stem- 



leaves, or (in Phyllocjlossum) with linear radical leaves Lycopodiaceae 9. 



D. Spore-cases of 2 kinds. 



Moss-like plants ; macrosporangia usually with 4 spores Selaginellaceae 10 

 Small plants with radical filiform leaves ; macrospor- 

 angia with numerous spores Isoetaceae 11. 



DIVISION 2.— SPERMATOPHYTA (Phanerogams). 

 Subdivision I.— GYMNOSPERMS. 

 Trees or shrubs with leaves like needles or scales ; ovules 

 naked on the upper surface of scales; fruit a hard cone 

 (Pines) Pin aceae 12. 



