404 



HUTCHINSON'S POPULAR BOTANY 



offer another typical form of irregular 

 flower, not only provide a platform, 

 but present their nectary to the 

 humble-bee directly he has taken his 

 seat ; the Aristolochias, which are 

 chiefly pollinated by flies, are furnished 

 with conveniences in the way of 

 perches and expansions for alighting, 

 which clearly save the little guests a 

 world of trouble. The Orchids (figs. 

 468 and 473) are provided with " all 

 sorts of lobings and sinuses, fringes, 

 pegs, and knobs on the lower lip, 

 which serve as landing-stages and as 

 fulcrum s for further explorations to 

 numerous flies, wasps, bees, humble- 

 bees, and butterflies." So one might 

 go on furnishing examples indefinitely. 

 The subject is inexhaustible, though 

 whether the irregularity should be 

 regarded as one of the causes of 

 insect visits, or whether it is merely 

 an effect, as Professor Henslovv would 

 persuade us, are questions which need 

 not be discussed in this place. 



The second provision in flowers for 

 the reception of insects comprehends 

 all those markings and accessory 

 growths on the sepals and petals 

 which are known as Honey-guides or 

 Path-finders. The beautiful pencillings 

 of flowers (spots, stripes, etc.), no less 

 than their bright colours, serve, it is 

 thought, to attract insects. Sprengel 

 maintained nearly a century ago that 

 the purpose of the marks is to guide 

 to the nectary, a notion which Darwin 

 for a long time scouted ; but when 

 the latter published his book on the 

 Effects of Cross and Self-fertilization in 

 ttte Vegetable Kingdom, he had come 

 round to Spren gel's view, and, indeed, 

 defended it therein. In Darwin's 

 opinion the case of the Pelargonium affords the best evidence that these 



FIG. 501. FLOWER OF SAGE (Salvia 



officinalis), 

 Showing the mechanism as set in motion by the visit 



