130 POLYMORPHY [CH. 



If, as occurs in the Ericaceae for instance, the actual 

 number of organs in each whorl varies in the different 

 genera, but the relative numbers are constant in the 

 flower, we can use a general floral formula thus: 



K ( n) C (n) | A n+n G(n) 



and add the values attached to n, in this case 4 or 5. 



The formula given still tells us that the flower is 

 actinomorphic, the calyx and corolla gamophyllous and 

 equally segmented, the stamens twice the number of 

 these segments, and free from the corolla, and the pistil 

 has the same number of carpels and is superior. 



Theoretical considerations show that such a flower 

 has the stamens displaced from the strictly alternate 

 position, and this ob-diplostemonous condition is denoted 

 by the sign which signifies that the outermost whorl of 

 stamens is opposite the petals, or rather, here, the 

 corolla lobes. 



Many other signs can of course be employed, but 

 enough has been said to explain the principles. It not 

 unfrequently happens that while most of the flowers are 

 of one kind and order of symmetry, terminal ones in an 

 inflorescence are different, as in the Rue, where most of 

 the flowers are 4\/ but the end one 5^ ; Adoxa, with the 

 terminal one 4\/ and the lateral ones 5\/> an d other cases 

 occur. In Acalypha indica the single $ flower which 

 terminates the mixed inflorescence has only one ovule, 

 and that unlike those of the other $ flowers. In the 

 Sycamore and other species of Acer, flowers with various 

 numbers are common in the inflorescence, and while the 

 lateral flowers are usually the terminal are <. The 

 central flower of the umbel of Daucus carota, the wild 

 carrot, is purple, the others white. Many other cases 

 of polymorphy of the flower are known. The terminal 

 flower of an inflorescence with zygomorphic flowers is not 



