A BOTANICAL DIFFICULTY. 221 



The observer is sometimes embarrassed in deciding to which 

 whorl he should refer the foliola he is examining. Thus, the 

 tiny foliola which, in the strawberry and the potentilla, alter- 

 nate with others and larger ones, are stipules rather than sepals. 

 Ought the sepals of the calyx in the Malvaceae to be assimi- 

 lated in like manner to the stipules ? It is difficult to reply 

 to this question satisfactorily. Take, for example, the Hibiscus 

 Syriacus, an ornamental shrub, better known by the name of 

 the garden-hemp. The inner calyx, or calyx properly so 

 called, of this Malvacea has five sepals, while the outer calyx, 

 or calicule, has twelve. Now, a leaf cannot have more than 

 two stipules, one on each side. For an outer calyx, then, 

 the proper number of foliola is ten, not twelve. To look 

 upon the second calyx as a "supernumerary development," 

 would be to hazard a supposition contrary to the unity of 

 plan of the floral organs. 



The calyx, like the corolla, is not an absolutely indispen- 

 sable organ. Sometimes, therefore, it is caducous that is, 

 falls off before the flower expands, as in poppies ; some- 

 times, persistent, or remains after flowering, as in roses and 

 the majority of plants. In some cases it is persistent only 

 until after the act of fecundation, but this act accomplished, 

 it falls with the corolla in most of the Cruciferae and Ranun- 

 cuiaceae. This is a deciduous calyx. 



The "caducity" and "persistency" of floral envelopes 

 furnish some valuable characteristics for the distinction 01 

 species. Thus ; two closely-allied Cruciferae, the Alyssum 



