FLORAL SYMMETRY, ETC. 137 



A GLOMERULE is a cymose cluster of sessile flow- 

 ers in the axil of a leaf (Fig. 291). 



What is known as compound inflorescence occurs 

 when the flower-clusters of a plant develop in one 

 way, and the plant itself develops in another way. 

 For instance, in Fig. 291 each cluster is definite, or 

 cymose, while the stem that bears them is indefinite. 

 This state of things is often met with. Compare the 

 development of the sunflower with that of catnip 

 and horehound in this respect. 



The indefinite mode of growth is sometimes spoken 

 of as centrifugal, because the flowers open first at the 

 circumference ; while definite forms are said to be 

 centrifugal, because here the flowers open at the cen- 

 tre first. 



EXERCISE XLVI. 

 Duration of Floral Envelops. 



The floral whorls are said to be CADUCOUS when 

 they fall off at the opening of the flower. Ex- 

 amples, calyx of the poppy, corolla of the grape- 

 vine. 



DECIDUOUS, when they fall before the fruit is 

 formed. 



PERSISTENT, when they remain till the fruit is 

 matured, as is frequently the case with the calyx of 

 inferior fruit. 



MARCESCENT, when they persist in a dry and 

 withered state. 



