Vlll KEY TO THE ORDERS. 



Endosperm wanting. PAGE 



Flowers regular, monoecious or dioecious: aquatic plants. 



Order HYDROCHARITALES. 46 

 Flowers irregular, perfectr terrestrial or epiphytic plants. Order ORCHIDALES. 308 



2. DlCOTYLEDONES. 



A. Corolla wanting, except in the pistillate flowers of Juqlans (Juglandaceae) . 



Calyx wanting, at least in the staminate flowers, except sometimes in Casuarina (Casuarinaceae) . 

 Herbs. 



Flowers mainly perfect. 



Seeds solitary in each carpel or in each cavity of the ovary: endosperm present. 



Flowers spicate: styles wanting: stigmas sessile. Order PIPERALES. 331 



Flowers axillary: styles present. Callitrichaceae in Order EUPHORBIALES. 690 



Seeds numerous in each cavity of the ovary: endosperm wanting. 



Podostemaceae in Order ROSALES. 494 



Flowers monoecious or dioecious. Order EUPHORBIALES. 690 



Trees or shrubs: flowers monoecious or dioecious, or polygamous. 



Leaves represented by appressed whorled scales: stems or branches loosely jointed. 



Order CASUARINALES. 332 



Leaves not appressed scales: stems or branches not loosely jointed. 

 Fruit 1-seeded: seeds without tufts of hairs. 



Ovules 1 or 2 in each cavity of the ovary: flowers not in heads. 



Gynoecium 1-carpellary : stigma 1: ovule laterally attached and amphitropous. 



Order LEITNERIALES. 335 

 Gynoecium 2-carpellary: stigmas 2: ovule erect and orthotropous or pendulous 



and anatropous. 

 Pistillate flowers without a calyx: ovule erect and orthotropous. 



Order MYRICALES. 336 



Pistillate flowers with a calyx: ovule pendulous and anatropous. 

 Leaf-blades simple. 



Fruit a nut or an achene. Corylaceae in Order FAGALES. 343 



Fruit a drupe. Oleaceae in Order OLEALES. 916 



Leaf-blades compound: fruit a samara. Oleaceae in Order OLEALES. 916 



Ovules many: flowers aggregated into dense heads. Altingiaceae in Order ROSALES. 494 



Fruit many-seeded: seeds each with a tuft of hairs. Order SALICALES. 338 



Calyx present at least in the staminate or in the perfect flowers. 



Leaves represented by appressed whorled scales: branches loosely jointed. 



Order CASUARINALES. 331 

 Leaves not appressed scales: branches not loosely jointed. 



Flowers, at least the staminate, in aments, or ament-like spikes. 

 Leaf-blades simple: ovule pendulous and anatropous. 



Pistillate flowers separate at maturity: fruit a nut or an achene. Order FAGALES. 343 

 Pistillate flowers forming aggregate fruits: fruit drupe-like. 



Artocarpaceae in Order URTICALES. 355 



Leaf-blades pinnately compound: ovule erect and orthotropous. Order JUGLANDALES. 332 

 Flowers, at least the staminate, not in aments. 

 a. Ovary superior. 



Gynoecium of 1 or several and distinct carpels: stigma and style solitary. 

 Carpel solitary. 



Style lateral and oblique. Petiveriaceae in Order CHENOPODIALES. 383 



Style axile, erect. 



Ovary neither enclosed nor seated in a hypanthium or a calyx-tube. 

 Flowers not solitary in axils: land plants. 



Filaments free and distinct. Urticaceae in Order URTICALES. 355 



Filaments adnate to the sepals or to the calyx-tube. 



Order PROTEALES. 819 

 Flowers solitary in axils: aquatic plants. 



Ceratophyllaceae in Order RANALES. 428 

 Ovary enclosed in or seated in a hypanthium or a calyx tube. 

 Stamens borne under the gynoecium. 



Allioniaceae in Order CHENOPODIALES. 383 

 Stamens borne on the hypanthium or adnate to the calyx-tube. 



Order THYMELEALES. 820 

 Carpels several. 



Stamens inserted below the ovary. Families in Order RANALES. 428 



Stamens inserted on the edge of a cup-shaped hypanthium. 



Rosaceae in Order ROSALES. 494 



Gynoecium of 2 or several united carpels: stigmas or styles 2 or several. 

 *Ovary, by abortion, 1-celled and 1-ovuled. 



Leaves with sheathing stipules (ocreae). Order POLYGONALES. 366 



Leaves estipulate, or if stipules are present they are not sheathing. 

 Trees or shrubs. 



Anthers opening by slits: ovary not seated in a hypanthium. 



Ulmaceae in Order URTICALES. 355 

 Anthers opening by hinged valves: ovary seated in an accrescent 



hypanthium. Lauraceae in Order THYMELEALES. 820 



Herbs or vines. 



t Leaves with stipules. 



Stipules herbaceous: inflorescence spicate or racemose: leaf-blades 



palmately veined. Cannabinaceae in Order URTICALES. 355 



Stipules scarious or hyaline: inflorescence cymose: leaf-blades pin- 

 nately veined. Families in Order CHENOPODIALES. 383 

 ft Leaves without stipules. 



Stigmas entire. Order CHENOPODIALES. 383 



