426 MINNESOTA BOTANICAL STUDIES. 



Puccinia Cypripedii' ^ Arth. and Holw., one of the rusts, af- 

 fects Cypripedium hirsutum Mill. 



The record of the period of persistence of individual flowers 

 in this genus is not extensive. A noteworthy instance is 

 that of Cypripedium villosum Lindl. 12 (Burma) in which they 

 were observed to last for ten days. This duration of flowering 

 is probably closely related to the peculiar method of pollination 

 which is characteristic of this genus. 



Mueller, Darwini^ and Gray are among the more recent ob- 

 servers on this point. One of the earliest workers to discover 

 that insects were necessary to remove the pollen masses in Or- 

 chids was Christian Konrad Sprengel,who published a valuable 

 work in 1793. Robert Brown also believed that insects were 

 the principal agents assisting in this process. ^^ According to 

 Darwin, many Orchids seem to be adapted for insects' visits, 

 especially such insects as possess a long proboscis. ^ ^ While 

 this was true of other Orchids, Cypripedium seemed to be the 

 exception, and A. Gray was instrumental in pointing out this 

 circumstance; 1^ he offered the suggestion that the action of 

 flies would better explain the mode of pollination. In the case 

 of Cypripedium, no nectar was in the drops adhering to the 

 hairs lining the base of the labellum, and the self-evident con- 

 clusion remained that the flowers were not visited for the sake 

 of the nectar. The flowers, indeed, are attractive in color, and 

 insects of various kinds have been found within the labellum of 

 some of the species. 



Sir John Lubbock's investigations relating to the color 

 motive of insects, has added interest in this case. ^ '^ He tested 

 bees for their appreciation of color by placing honey on glass 

 over colored paper. Beginning with the single color blue, 

 other colors were introduced and transposed. Yellow and blue 

 were interchanged, and the bees were found to leave untouched 

 the honey over the yellow color and would fly to the blue. 

 "Flowers of yellow or fleshy color were most attractive to 

 flies." 18 



He also found that bee flowers have generally bright, clear 

 colors, while fly flowers are usually reddish or yellowish brown, ^ ^ 



(11) Farlow and Seymour. Host. Index N . Am. Fungi, 1-3: 135. 1888, 1891. 



(12) Kerner and Oliver. Nat. Hist. PI. 253. 1893. 



(13) Darwin, C. Fertilization of Orchids. Ed. 2. 1877. 



(14) Darwin C. Loc. cit. 3. 



(15) Darwin, 0. Am. Jour. Sci. 34: 428, 18e2. 



(16) A.Gray. Papers ]862-18r3. 



(17) Lubbock J. Flowers, Fruits and Leaves. 13. 1894. 



(18) Lubbock, J. Loc. cit. 14. 



(19) Lubbock J. Loc. cit. 43. 



