62 SCIENCE PRIMERS. [xin. 



double cherry, in which the carpels appear as green 

 leaves. 



87. The number of sepals, petals, and stamens is 

 in Dicotyledonous plants, most frequently 4 to 5 each, 

 or a multiple of that number ; whereas 3 or a multiple 

 of that number prevails in Monocotyledons; which 

 is the fourth means of distinguishing plants of this 

 class (see Pars. 39, 53, 60, 73). 



XIII. THE CALYX. 



SEPALS. 



88. The calyx is formed of a whorl of free or com- 

 bined organs called sepals. It is usually green and 

 leaf-like in texture, and it often persists in the fruit. 

 Its use is to protect the parts of the flower within it. 



89. Although the outermost of the floral whorls, the 

 calyx is sometimes placed at a higher level than the 

 ovary. This is because either the ovary is sunk in the 

 swollen top of the peduncle (rose, Fig. 31); or because 

 the surface of the sepals adheres more or less to the 

 sides of the ovary, their free parts spreading out above 

 it. Hence the employment of the terms calyx superior 

 and calyx inferior, which are equivalent respectively 

 to ovary inferior and ovary superior (Par. 84 d ). 



90. The sepals of the calyx may be free from one 

 another, when the calyx is polysepalous (butter-cup, 

 Fig. 22) ; or combined, when it is monosepalous (prim- 

 rose, Fig. 28). 



91. The most curious form of calyx that commonly 

 occurs is that of the dandelion, groundsel, thistle, 



