ANALYTICAL KEY. 
xxvn 
Ovary plainly free from the calyx, which is sometimes wanting. 
Stipules (ocreae) sheathipg the stem at the nodes: 
Tree , calyx none ; flowers monoecious in heads. Platanaceae. 
Herbs; calyx present and commonly petal-lilce. Polygonace^e, 72 
Stipules not sheathing the stem, or none : 
Aquatic herbs, submerged or nearly so : 
Leaves whorled and dissected ; style single. 
CeRATOPHYLLACEAE. 
Leaves opposite, entire; styles 2, ovary 4-celled. 
Halorage^e. 
Not aquatic, herbs : 
Ovary 10-celled; berry 10-seeded . . Piiytolaccaceae, 72 
Ovary 3 (rarely l-2)-celled ; juice usually milky. 
Eupiiorbiaceae, 77 
Ovary 1-celled; juice not milky. 
Style, if any, and stigma only one; leaves simple; 
no scarious bracts around the flowers. . Urticaceae, 78 
Style or stigma 2 or 3; embryo coiled or curved. 
Stipules not scarious, leaves palmately cleft or 
palmately compound. Cannabineae in Urticaceae, 78 
Stipules scarious (or none) ; leaves opposite. 
Illecebrace^e. 
Stipules none, but flowers with scarious bracts. 
Amaranth aceae. 
Stipules and scarious bracts none. CiienopodiacejE, 71 
Shrubs or trees : 
Ovules a pair in each cell of the ovary. 
Fruit 2-celIed, a double samara. . . Acer in Sapindaceae. 
Fruit a 1-celled and 1-seeded samara or drupe. . Oleace^e, 51 
Ovules single in each cell of the 
Three-celled ovary; leaves broad. . . Rhamnace^e, 15 
One-two-celled ovary; styles or stigmas 2-cleft. Urticaceae, 79 
One-celled ovary; style and stigma single and entire. 
Anthers opening longitudinally. . . Tiiymelaeace^e. 
Anthers opening by uplifted valves. . . Laurace^e, 75 
B. Flowers monoecious or dioecious, one or both sorts in catkins. 
1. Only one sort of flowers in catkins, or catkin-like heads. 
Fertile flowers in a short catkin, head or strobile. Urticaceae, 78 
Fertile flowers single or clustered, sterile in slender catkins (ex- 
cept in Fagus). 
Leaves pinnate; fertile flowers and fruit naked. Juglandace^e, 80 
Leaves simple ; fertile flowers 1-3 in an involucre or cup. 
OuPULIFERAE, 81 
