XIV] 



IRREGULAR FLOWERS 



125 



In descriptive field-botany it is usually regarded as 

 sufficient to say whether the flower is regular or irregular, 

 biit observation brings out that there are several types of 

 each. Thus, the flowers of a Crucifer (Fig. 31), a Fuchsia, 

 a six-petalled Sedum, and a Gentian are all regular, but the 

 Crucifer is also isobilateral ; it can be divided into sym- 

 metrical halves in two planes at right-angles, but the 

 halves in one plane are unlike those in the other. In the 

 cases of the Fuchsia and the six-petalled Sedum, there 

 are four and twelve planes respectively, half giving 

 similar halves of one kind, and half giving those of the 

 other kind, and these instances can easily be multiplied 

 by the student. In the Gentian only one plane can be 

 found in which perfectly similar sections result, because 

 there are only two carpels ; but although it may be 

 argued that such a flower is strictly not actinomor- 

 phic but zygomorphic, no field-botanist would term it 

 irregular. 



Fig. 31. Floral diagram of 

 a Crucifer. The flower is 

 regular, but isobilateral (Ei). 



Fig. 32. Floral diagram of 

 Orchis, before resupination. 

 LAB. = labellum, STD. = stami- 

 node (Ei). 



In similar manner, when we come to irregular flowers, 

 several cases occur in addition to the one described. The 

 flower of Dicentra is irregular, but bilateral : that of a 

 Valerian or Canna is asymmetric, in so far that there is 



