MANUAL OF THE FLOWERING PLANTS OF IOWA. 



ANALYTICAL KEY TO THE FAMILIES. 



Series 1. Phanerogams or Flowering Plants: those producing trae 



flowers and seeds. 

 Class 1. Angiosperms: plants which have the ovules contained in a 



closed ovary. 

 Subclass 1. Dicotyledons: stems differentiated into bark, wood, and 

 pith; leaves netted-veined; embryo with a pair of opposite cotyle- 

 dons; flowers usually 4 or 5-merous. 

 Division 1. Polypetalae: calyx and carolla present, petals separate. 

 Apetalous forms occur as will be noted farther on. 

 The following wholly artificial key is taken from various governmental 

 publications and adapted to the Iowa flora. 



A. Stamens ten to many and more than twice the number of sepals. 

 * Calyx entirely free from the ovary. 

 Pistils many, distinct, enclosed in a hollow receptacle; leaves alternate, 



stipulate. Rosa, in Rosaceae, 4'.i. 



Pistils several, contained in pits on the upper surface of » large convex 



receptacle. Nelumbo, in Ni'mpi-iaeaceae, 7. 



Pistils more than one, distinct, not enclosed in the receptacle. 



Stamens inserted on the edge of a disk which lines the calyx-tube, dis- 

 tinct; anthers' 2-celled. Rosaceae, 44. 

 Stamens monoJelphous, united with the base of the petals; anthers 1- 



celled. Malvaceae, 23. 



Stamens inserted on the receptacle. 



Small trees; filaments shorter than the anthers. Anon aceaE, 6. 



Herbs or woody climbers; filaments longer than the anthers. 

 Flowers dioecious; twiners; leaves alternate, palmately lobed. 



Menispebmaceae, 7 

 Flowers perfect, if climbers the leaves are opposite. 

 Leaves peltate; petals persistent. 



I'rasenia, in Nymphaeaceae, 7. 

 Leaves not peltate; petals deciduous. Ranunculaceae, 1. 



Pistils several-lobed, the ovaries united below the middle. 



RESED ACEAE, 16. 



Pistils several, their ovaries cohering in a ring around an axis. 



Malvaceae, 23. 

 Pistil solitary as to the ovary but styles or stigmas may be several 



Leaves punctate with pellucid or black dots. Hypericaceae, 22. 



Leaves not punctate with pellucid or black dots. 



Ovary simple, 1-celled, 2-ovuled; fruit a drupe. Drupaceae, 43. 

 Ovary simple, 1-celled, several-ovuled; fruit a legume. 



Mimosaceae, 43. 

 Ovary compound, 1-celled; placenta central. Portulacacbae, 21. 



