150 Mr, C. Darwin on the Fertilization of Orchids. 



labellum plays an important part in leading insects to enter 

 and leave the flower in a proper manner for fertilization. 



Fertilization o/Epipactis latifolia (p. 104). — Although this 

 orchis is not common in the vicinity of Down, by a fortunate 

 chance several plants sprang up in a gravel walk: close to my 

 house, so that I have been able to observe them during several 

 years, and have thus discovered how they are fertilized. Al- 

 though hive-bees and humble-bees of many kinds were con- 

 stantly flying over the plants, I never saw a bee or any Dip- 

 terous insect visit the flowers ; whilst, on the other hand, I 

 repeatedly observed each year the common wasp ( Vespa syl- 

 vestris) sucking the nectar out of the open cup-shaped label- 

 lum. I thus saw the act of fertilization eflfected by the pollen- 

 masses being removed and carried on the foreheads of the 

 wasps to other flowers. Mr. Oxenden also informs me that 

 a large bed of E. purpurata (which is considered by some 

 botanists a distinct species, and by others a variety) was 

 frequented by "swarms of wasps." It is very remarkable 

 that the sweet nectar of this Fpipactis should not be attractive 

 to any kind of bee. If wasps were to become extinct in any 

 district, so would the Epipactis latifolia. 



Dr. H. Muller of Lippstadt has published (Verhandl. d. Nat. 

 Ver. Jahrg. xxv. III. Folge, v. Bd. pp. 7-36) some very im- 

 portant observations on the differences in structure and in the 

 manner of fertilization, as well as on the connecting gradations, 

 between Epipactis ruhiginosa^ microphylla^ and viridiflora. 

 The latter species is highly remarkable by the absence of a 

 rostellum, and by being regularly self-fertilized. This latter 

 circmnstance follows from the incoherent pollen of the lower part 

 of the pollen-masses emitting, whilst still within the anther- 

 cells, pollen-tubes, which penetrate the stigma ; and this oc- 

 curred even in the bud state. This species, however, is probably 

 visited by insects, and occasionally crossed ; for the labellum 

 contains nectar. E. microphylla is equally remarkable, by 

 being intermediate in structure between E. latifolia^ which is 

 always fertilized by the aid of insects, and E. viridiflora^ 

 which does not necessarily require any such aid. The whole 

 of this memoir by Dr. H. Muller deserves to be attentively 

 studied. 



Cephalanthera grandiflora (p. 108). — During the year 1862, 

 the flowers of this orchis appeared to have been visited much 

 less frequently by insects than during the previous years ; for 

 the masses of pollen were seldom broken down. Although I 

 have repeatedly examined the flowers, I have never seen a 

 trace of nectar ; but some appearances lead me to suspect that 

 the ridges within the base of the labellum are attractive to 



