vi KEY TO the; FAMILIES 



Subclass 2. DICOTYLEDONES. 



Leaves mostly netted-veined ; flowers seldom 3-merous or 6- 



merous, usually 4-merous or 5-merous, 



Petals separate and distinct from each other or some- 

 times wanting, rarely somewhat united. Series 1. Choripetalae. 



Petals partly or wholly united, rarely separate or 



wanting. Series 2. Sympetalae. 



Series i. CHORIPETALAE. 



Petals distinct, at least at base, except in some species of Montia, 

 Silene and Crassulaceae. 



Petals wanting. 



(A) Flowers unisexual, one or both kinds in aments; trees or shrubs. 



Staminate flowers in aments, pistillate becoming a 

 nut. 

 Leaves pinnate. Juglandaceae, 93. 



Leaves entire or variously lobed or toothed. Fagaceae, 95. 



Staminate and pistillate flowers both in aments. 



Leaves opposite; flowers dicecious. Garrya, 268. 



Leaves alternate. 



Flowers dioecious; fruit a capsule. Salicaceae, 89. 



Flowers monoecious; fruit not a capsule. 



Pistillate flowers becoming wax-coated 



berries. Myricaceae, 92. 



Pistillate flowers with their scales becom- 

 ing a woody cone. Betulaceae, 94- 



(B) Flowers not in aments. 



* Ovary superior. 



1. Herbs. 



Calyx and corolla both wanting. 



Flowers perfect, in spikes, these surrounded at base by 



a conspicuous white involucre. Saururaceae, 88. 



Flowers monoecious. 

 Aquatic plants. 



Leaves dissected. Ceratophyllaceae, 137. 



Leaves entire. Callitrichaceae, 216. 



Terrestial plants; flower-clusters surrounded by a 

 petaloid involucre; ovary 3-celled, raised above 

 the staminate flowers; the whole appearing as a 

 single flower. Euphorbiaceae, 211. 



Calyx present; corolla wanting. 



Pistil 1. 



Ovary 1 -celled, 1-ovuled. 

 Stipules present. 

 Leaves alternate. 



Stipules not sheathing. 



Flowers monoecious; herbage with 



stinging hairs. Urticaceae, 98. 



Flowers perfect, fascicled; diminu- 

 tive annual. Alchemilla, 183. 

 Stipules sheathing; calyx usually 6- 



parted, often petaloid. Polygonaceae, ioi. 



Leaves opposite, pungent; petals repre- 

 sented by minute scales. Pentacaena, 137. 

 Stipules none. 

 Calyx petaloid. 



Calyx 6- (rarely 5-) parted; seed a 3- 

 sided or lenticular achene. Polygonaceae, ioi. 



