70 ACHLAMYDEOUS FLOWERS, ETC. [CH. 



with the petals gradually becoming smaller and smaller 

 until none are developed at all e.g. G. vulgatum ; or it 

 mny be a primitive condition, where petals have never 

 been developed at all, as is probably the case in the Oak, 

 Beech, Hazel, &c. In practice, in the field, these two 

 conditions of affairs cannot be distinguished for systematic 

 purposes, though theoretically they must be sharply dis- 

 tinguished, and are of importance in systematic botany : 

 each case must be judged by comparison with allied 

 forms. 



The following afford examples of achlamydeous 

 flowers : 



Willows Birch Sweet Gale 



Ash Poplars Alder, 



though male flowers in the Alder and Birch are mono- 

 chlamydeous. 



In the case of the Gymnospermous flower it is not 

 usual to refer to the presence or absence of the perianth ; 

 but if the barren scales at the base of the cone represent 

 an incipient perianth the flowers are monochlamydeous. 

 If not, then they are achlamydeous. 



The following afford examples of monochlamydeous 

 flowers : 



In most of these cases, therefore, we speak of a 

 perianth or 2)erigone rather than of calyx or corolla : 

 strictly speaking, the envelope is a perianth if enclosing 



