THE FORMS OF FLORAL ORGANS. 105 



Compensating processes tlius come into play, so tbat 

 while some parts are enlarged others are diminished, the 

 former always having to bear the strains, while the latter are 

 free from them. Thus the lip of Lamium consists of one 

 much-enlarged petal, which forms an excellent landing-place, 

 but the two lateral jjetals, not being required, are atrophied 

 to mere points. Similarly, while the two posterior petals 

 enlarge to form the hood, presumably due to the backward 

 thrust of the insect's head, the posterior stamen has vanished 

 altogether. The gamosepalous calyx nosv furnishes its aid 

 to support the slender tube of the coi'olla, not only by 

 doubling its number of ribs, but by uniting them all together 

 by means of a sclerenchymatous cylinder within the mesophyl. 



If the tube of the corolla be very strong and well able 

 alone to support the insect, the adhesion of the filaments 

 being also a powerful addition to its strength, then the calyx 

 often remains polysepalous, as occurs in the Foxglove, 

 Snapdragon, Petunia, etc. 



If, instead of the anterior petal forming the landing- 

 place, the tube of a gamopetalous corolla has enlarged so as 

 to admit the ingress of an insect which partly or entirely 

 crawls into it; then it is this tubular part which, moi-e 

 especially having to bear the strain upon it, bulges outwards, 

 or becomes more or less inflated in form ; while the lip or 

 anterior petal, not having to bear the entire burden, is not 

 particularly enlarged, if it be at all. The Foxglove and 

 Gloxinia, as well as Petunia to a slight extent, illustrate this 

 adaptation in irregular flowers, while "campanulate" flowers 

 afford examples amongst regular ones. 



gravitation can act in any otlier way than " downwards." Bat if one 

 observes how a humble-bee suspends itself on the stamens while its 

 body, so to say, thrusts the petals aside and upwards, we find a much 

 more satisfactory interpretation in the theory I have proposed. 



