KEY TO THE FAMILIES. 



27 



Class 2.— DICOTYLEDONS. 



Subclass 1. — Archichlamydeae. 

 Plants whose perianth occupies a lower stage of development. Some have neither calyx 

 nor corolla (achlamydeous) ; others have a perianth which is all either petal-like or sepal- 

 like, and may be simple (haplochlamydeous, monochlamydeous) or double (diplochlamydeous), 

 and in the latter case the 2 whorls may be dissimilar (sepals and petals), and the petals 

 are then usually separate from each other (choripetalous flower). 



There arej however, some exceptions. The petals are more or less united (usually near 

 their bases) in Stackhousia, Fumaria, and Olax, in many Acacias, in Polygalaceae, Papilion- 

 atae, Malvaceae, and Oxalidaceae, and in some genera of Pittosporaceae and Rutaceae. 

 The petaloid segments of Loranthus and of Proteaceae and Nyctaginaceae are also more or 

 less united. Petals are sometimes absent in a particular genus, although they may be 

 characteristic of the family ; such cases are Pomaderris (Rhamnaceae), Brachychiton 

 (Sterculiaceae), Dodonaea (Sapindaceae), and some genera of Euphorbiaceae, Rosaceae, and 

 Lythraceae. 



1. Ovules with many embryo-sacs (macrospores). 

 Order V erticillatae. 



Flowers unisexual ; male flowers in catkins ; female 

 without perianth ; fruit a cone ; leaves reduced to 

 whorls of small teeth (Sheoak) Casuarinaceae 33. 



2. Ovules with usually only 1 embryo-sac. 



. Flowers naked or with a simple bract-like perianth. 



Order Urticales. Flowers unisexual ; perianth of usually 

 4 segments ; carpel 1 ; ovary superior, 1-ovuled ; 

 albumen scanty. 

 Trees with milky sap ; flowers enclosed in a hollow 



receptacle which becomes the fruit (fig) Moraceae 34. 



Herbs with opposite leaves and stinging hairs (Nettle). . Urticaceae 35. 



. Flowers with a simple or double bract-like or sometimes 

 petaloid perianth. 



B. Order Proteales. Perianth simple, petaloid ; stamens 4, 

 inserted on the 4 segments; carpel 1, superior; nut, 

 drupe, or hard follicle ; seed exalbuminous (Needle- 

 bushy Banksia) Proteaceae 36. 



B. Order Santalales. Flowers regular ; carpels 1-3 united ; 

 ovary 1 -celled, usually inferior ; seeds albuminous. 



C. Perianth-segments in 1 whorl, petaloid ; flowers 



bisexual or unisexual ; parasites. 



Segments 4-5, with the same number of stamens 



opposite them ; ovary 1 -celled, with 2-5 ovules on 



a central placenta ; nut, drupe or berry ; shrubs 



or trees (Quandong, Native Cherry) Santalaceae 37. 



Segments 4-6, free or united, with the same number 



of stamens inserted on them ; ovary inferior, 



1 -celled, 1-ovuled ; berry sticky ; leaves opposite 



(Mistletoe) Loranthaceae 39. 



C. Perianth-segments in 2 whorls ; calyx 4-6-toothed ; 



petals 4-6 ; ovary superior ; drupe ; shrub Olacaceae 38. 



B. Order Polygonales. Perianth-segments 3-6, herbaceous, 

 in 1 or 2 whorls ; flowers regular, bisexual or unisexual ; 

 stamens 6-9 ; ovary superior, 1 -celled, 1-ovuled, with 

 2-4 styles ; embryo usually straight ; angular nut ; 

 stipules sheathing the stem ; herbs or shrubs (Dock, 



Knot grass, Lignum) Polygonaceae 40. 



B. Order Centrospermae. Flowers regular ; stamens usually 

 as many as and opposite the perianth-segments ; ovary 

 usually of several united carpels, 1 -celled, with 1 or more 

 ovules ; embryo usually much curved round the 

 albumen, which is sometimes absent. 



D. Perianth simple, except in some Aizoaceae. 



E. Flowers bisexual or unisexual ; ovary superior. 



Perianth herbaceous, of 1-5 lobes or segments ; 

 stamens opposite segments ; ovary 1 -celled, with 

 1 basal ovule ; styles 2-3 ; flowers small, some- 

 times immersed in fleshy branches ; herbs or 

 undershrubs (Goosifoot, Saltbush, Samphire) . . . . Chenopodiaceae 41. 



