INTRODUCTION TO TIIE REPORTS ON INSULAR FLORAS. 



27 



eastward to Amsterdam and the Macdonald group. The Bermudas possess three ; Falk- 

 lands, seven ; Juan Fernandez, two ; the Galapagos, three ; and the proportion is small in 

 most insular groups. Orchids are singularly scarce in insular floras ; yet they are so 

 widely dispersed, nearly reaching the polar limits of flowering plants, and occupy such 

 a variety of soils and situations, that their rarity in oceanic islands would seem to be 

 due rather to secondary than primary causes. 1 In illustration of this phenomenon, we 

 append a table showing the absence, or number of species inhabiting various islands. 



Orchide^e in Insular Flc^^s. 



The fore^oinc; selection of islands and islets covers a wide area of the globe, and 



1 How far the absence, or rarity, of Leguminosce, Gymnospermeas, and Petaliferous Monocotyledons in 

 oceanic islands, and of the first in the Antarctic regions, may be accidental or due to climatal conditions, is 

 conjectural ; the concomitant rarity of insects, however, is a very probable reason so far as the first and last are 

 concerned ; but we know too little of the interdependence of plants and insects generally. From the observations 

 of Darwin, Delpino, H. and F. Mueller, and others, it appears certain that fertilisation without insect agency 

 is impossible in many plants, and especially so in a large number of the Legurninosae and Orchidese. Gymno- 

 spermea?, on the other hand, are anemophilous. Further, if the seeds of any flowering plants be transportable 

 very long distances by winds, it is those of orchids, for they are most exceedingly minute and light ; and they 

 are produced in astonishing numbers. Darwin (Ann. and Mag. Nat. Hist., ser. 4, vol. iv. p. 158) mentions 

 that it had been calculated that a single plant of Acropera probably sometimes produced as many as seventy- 

 four millions of seeds in one year ; and Fritz Mueller estimated the number of seeds in one capsule of a 

 Maxillaria at 1,756,440 ! 



2 Groenlund (Botanisk Tidsskrift, 2, iv. p. 57) places the sign of doubt before seven of the species recorded 

 by various authors, and suggests that some of them at least have been wrongly named, or erroneously attributed 

 to Iceland. He is most likely right in some instances ; but with regard to Listera ovata, which he questions, 

 the specimen authenticated by Paulsen exists in the Kew Herbarium. Martins records seven species from 

 the Faeroes. 



