MODIFICATIONS OF THE FLORAL ORGANS. 179 



the nature and extent of the soldering, may be easily detected. 

 For example, if the number of petals or divisions of a mono- 

 petalous corolla do not correspond to those of the calyx, and 

 this difference is due to the cohesion of one or more of the 

 petals, the nature of the soldering may be readily detected by 

 the number of the midribs. Thus when two petals have united 

 in the place of one nerve, we shall detect two collateral nerves 

 in the petal, or three, one of which will be in the middle when 

 the compound petal results from the union of three petals. In 

 general, the number of midribs in the compound petal or sepal 

 will be sufficient to show the number of separate pieces which 

 have become soldered together. 



Let us take for illustration and analysis, the flower of the 

 common Snap-dragon (Linaria,) (Fig. 81.) The calyx is mo- 

 Fig. 81. 





nosepalous, and has five equal divisions. The corolla is mono- 

 petalous with two unequal lips, of which the superior repre- 

 sents two petals, the inferior, three, whose midrib is prolonged 

 into a spur. The stamens are four in number, two long, and 

 two short; the former being situated between the middle petal 

 and the two lateral petals of the lower lip, the latter being 

 placed in the fissures which separate the two lips. At the base 

 of the superior lip may be detected a little filament represent- 

 ing the fifth stamen. 



