STRUCTURAL BOTANY. 



Trimerous flowers are characteristic of this great group of Plant i s, 

 while pentamerous flowers commonly distinguish the Kxogens. 



66. Deficiencies often occur, rendering the flower incom- 

 plete. Such flowe v s lack some one or more entire sets of organs 

 When only one of the floral envelopes, the calyx, exists, the 

 flower is said to be apetalpus or moncchlamydeous (^Xa,u.Cf, a 

 cloak), as in Elm, Phytblacca. These terms are also loosely ap- 

 plied to such plants as Rhubarb, Anemone, Liverwort, where the- 

 pieces of the perianth are all similar, although in two or three 

 whorls. When the perianth is wholly wanting, the flower i* 

 said to be achlamydeous, or naked, as in Lizard-tail (15). 



18 



16 



16, Flower of Saururus (Lizard-tail) achlamydeous. 16, Flower of Fraxinu (Ash). 17, Flower u' 

 <5'ix (Willow), staminate 18, pistillate. 



67. Imperfect flowers are also of frequent occurrence. The) 

 are deficient in respect to the essential organs. A sterile or 

 staminate flower (denoted thus $ ) has stamens without pistils. 

 A fertile or pistillate flower (?) has pistils without stamens. 

 Such flowers being counterparts of each other, and both neces- 

 sary to the perfection of the seed, must exist either together 

 upon the same plant or upon separate plants of the same 

 In the former case the species is monoecious ( 8 ), as in Oak ; 



19. Pistillate flower of Blm ot-Gilead. 20. Stamtaate. 21. Begonu -u. staminate; I pistillate 



