MALADIE ET SYMBIOSE 283 



Epipactis viridi-flora, according to Darwin, is regularly self- 

 fertilised. Spiranthes austmlis, an inhabitant of Australia, 

 fertilises itself as regularly as does Ophrys apifera. Lister a ovata, 

 the Tway-blade, according to Darwin, one of the most remarkable 

 in the whole order (Neotteae), is visited by small Hymenopterous 

 insects and also by Diptera. Darwin's son was " struck with 

 the number of spider-webs spread over these plants, as if the 

 spiders were aware how attractive the Listera was to insects." 

 As regards this latter observation, we have here indeed, I believe, 

 evidence of a vicious circle of morbid " awareness " a perversion 

 of symbiotic " awareness." And the basis of this low kind of 

 " awareness " is this : the common desire, for in-feeding. Birds 

 of a feather flock together. 



Of the " unnatural sickly looking " Neottia-nidus-avis, Darwin 

 merely remarks that : 



the labellum secretes plenty of nectar, which I mention merely as a caution, 

 because during one cold and wet season I looked several times and could 

 not see a drop, and was perplexed at the apparent absence of any attrac- 

 tion for insects ; nevertheless, had I looked more perseveringly, perhaps 

 I should have found some. 



Probably Diptera are instrumental in removing the pollinia. 

 However, " a good deal of friable pollen is often left behind in 

 the anther-cells and is apparently wasted." " The spreading of 

 the pollen seems to be in part caused by the presence of Thrips, 

 many of which minute insects were crawling about the flowers, 

 dusted all over with pollen." 



The minute crawling insects assure " self-fertilisation," 

 " should larger insects fail to visit the flowers " and apparently 

 these do fail. Thelymitra carnea, another member of the Neotteae 

 " invariably fertilises itself by means of the incoherent pollen 

 falling on the stigma " ; the flowers " seem tending towards a 

 cleistogene condition." 



Amongst Cattleya we are told that self-fertilisation is pretty 

 frequent, whilst others are imperfectly fertilised by insects. A 

 curious instance of a " nectar-de-luxe " is furnished by Darwin 

 in the case of Cory ant hes, belonging to the " immense tribe of 

 the Vandeae, which includes many of the most magnificent pro- 

 ductions of our hothouses." 



What is secreted is a limpid fluid " so slightly sweet that it 

 does not deserve to be called nectar, though evidently of the same 

 nature ; nor does it serve to attract insects," and we are provided 



