28 OPHKE^. Chap. I. 



alight on the opposite sepals and petals. As a con- 

 sequence of this, when a butterfly inserts its proboscis 

 into the narrow entrance of the nectary, the yiscid discs 

 become attached to the lower surface of the proboscis, 

 and the pollinia afterwards move upwards, instead of 

 as in all other orchids downwards. They are then in 

 the proper position for striking the stigma of the next 

 flower which is visited. Dr. Miiller remarks that the 

 flowers are frequented by an extraordinary number of 

 butterflies. 



I have now described the structure of most of the 

 British and of a few foreign species in the genus 

 Orchis and its close allies. All these species, with the 

 exception of the Neotinea, require the aid of insects for 

 their fertilisation. This is obvious from the fact that 

 the pollinia are so closely embedded in the anther-cells, 

 and the ball of viscid matter in the pouch-formed 

 rostellum, that they cannot be shaken out by violence. 

 We have also seen that the pollinia do not assume the 

 proper position for striking the stigmatic jurface until 

 some time has elapsed; and this indicates that they 

 are adapted to fertilise, not their own flowers, but those 

 on a distinct plant. To prove that insects are neces- 

 sary for the fertilisation of the flowers, I covered up 

 a plant of Orchis mono under a bell-glass, before 

 any of its pollinia had been removed, leaving three 

 adjoining plants uncovered ; 1 looked at the latter 

 every morning, and daily found some of the pollinia 

 removed, till all were gone with the exception of those 

 in a single flower low down on one spike, and of those 

 in one or two flowers on the summits of all the spikes, 

 which were never removed. But it should be observed 

 that when only a very few flowers remain open on the 

 summits of the spikes, these are no longer conspicuous, 



