INSECTS AND FLOWERS 235 



for the sake of wetting their wings, and thus compelling 

 them to crawl out through the passage." 



The second example relates to orchids of the genus 

 Catasetum, in which the pollinia and the stigmatic sur- 

 faces are in different flowers, self-pollination being thus 

 out of the question. The pollinia are furnished with 

 viscid discs of huge size, but these are not so placed that 

 they would be likely to touch and adhere to an insect 

 visiting the flower. Indeed, there is nothing in the 

 chambered portion of the flower likely to attract insects. 

 "How then does Nature act?' asks Darwin. "She has 

 endowed these plants with . . . the remarkable power 

 of forcibly ejecting their pollinia even to a considerable 

 distance. Hence, when certain definite points of the 

 flower are touched by an insect, the pollinia are shot forth 

 like an arrow, not barbed however, but having a blunt and 

 excessively adhesive point. The insect, disturbed by so 

 sharp a blow, or after having eaten its fill, flies sooner or 

 later away to a female plant, and, whilst standing in the 

 same position as before, the pollen-bearing end of the 

 arrow is inserted into the stigmatic cavity, and a mass of 

 pollen is left on its viscid surface. Thus, and thus alone, 

 can the five species of Catasetum which I have examined 

 be fertilised." Small wonder that Darwin should have 

 regarded these flowers as "the most remarkable of all 

 orchids." 



Like the flowers of the orchids, those of the so-called 

 milkweeds {Asclepiadacece) of the New World are wonder- 

 fully designed with reference to cross-pollination by 

 insects ; but in these cases the flowers are regular. Pro- 

 fessor J. W. Folsom gives the following account of the 

 manner in which cross-pollination is effected : " As a 

 honey-bee or other insect crawls over the flowers to get 

 at the nectar, its legs slip in between the peculiar nectari- 



