72 Dr W. Rutherford on the Fertilisation of Orchids, 



separate, tliat is, unattached at the base to one another, the 

 right pollinium was removed rather oftener than the left, a 

 fact which would be difficult to explain. Of the 166 flowers 

 which had only one pollinium removed, 142 were fertile and 

 24 non-fertile, showing that where only one pollinium is re- 

 moved, the flower is not so certainly fertilised ; in short, the 

 insects have not visited them so frequently. 



It is unnecessary for me to comment further upon the 

 following Table, but I may shortly state, that it fully bears 

 out Mr Darwin's conclusions ; it establishes nothing new, 

 but simply places beyond doubt very important opinions 

 advanced by Darwin, among which the following are the 

 most important : — 1st, Insect agency is necessary for ferti- 

 lisation ; 2(i, Crossing of the individuals of a species is not 

 only permitted, but all the arrangements seem especially 

 adapted to bring about such a result. 



One would suppose that hybrids ought to be very com- 

 mon if Mr Darwin's opinion were correct, — that one insect 

 visits several species of orchids, — while it is well known that 

 orchidaceous hybrids are extremely rare. From all that I 

 have observed, I believe it to be the rule that each species 

 has its special visitor, and that the same insect visits several 

 species, to be the exception. I dare not, however, speak 

 too positively on this point, for my observations have not 

 been extensive. 



Finally, it may seem superfluous for me to draw attention 

 to the beautiful and laborious investigations contained in 

 Mr Darwin's work on orchids ; but only those who have 

 carried on such researches are able to estimate the severe 

 and prolonged labour which they entail. 



