228 VARIETIES OF THE COROLLA. 



The polypetalous corolla, as well as the gamophyllous 

 corolla, may be regular or irregular, according as the foliola 

 are equally or unequally united. But here again we must be 

 careful not to lay down too absolute rules. Examine, for 

 instance, the gamophyllous corolla of the gentians ; their two 

 lobes are very unequal, and yet the corolla is regular : five 

 very large lobes alternate with five very small, in such wise 

 that each of the latter is situated between two larger lobes. 

 Each division of the corolla of the periwinkle is irregular, 

 and yet the aggregate of their divisions is regular : these are 

 all of the same form and the same size. 



In the gamophyllous corolla we are able to discern, through 

 the different forms it assumes, the form of the parts which 

 compose the union. Thus, for example, the tubulate corolla 

 supposes the pre-existence of unguiculate petals. \ ' 



Inequality of union produces the bilabiate corolla, which is 

 invariably tubular. This is the case in the natural family of 

 the Labiatse. The upper lip is composed of two petals, and 

 the lower of three. The parts of the upper are sometimes 

 so closely joined that they appear to be but one, as in the 

 Lamium; and the lower often becomes quadrilobed by the 

 division of the middle petal, as in the Stacha. 



In the labiated corolla, the mouth of the tube is open, 

 while in the personate or masked (persona, a mask) it is 

 closed by the pressure of the lower lip against the upper ; as 

 in Snapdragon and Frogsmouth, the projection of the lower 

 lip being called the palate. By this feature the family of 



