SECT. XIII. 



ORCHIS PYRAMIDALIS. 



393 



would exactly strike the surface of the stigma when the 

 insect inserts its proboscis into the nectary of a flower. 



It was long ago noticed by Eobert Brown, that the 

 stigma is very viscid, but not so viscid as when touched 

 to pull the whole pollinium off the insect's head, yet 

 sufficiently viscid to break the elastic threads by which 

 the packets of pollen grains are tied together, and leave 

 some of them on the stigma. Hence a pollinium attached 

 to an insect can be applied to many stigmas, and fertilize 

 them all. Mr. Darwin mentions having seen the pol- 

 linium of Orchis pyramidalis adhering to the proboscis 

 of a moth with the stalks alone left, all the packets of 

 pollen having been left glued to the stigma of the flowers 

 successively visited. It appears that insects, for the 

 most part, only remove one pollinium at a time, and that 

 the rostellum returns to its normal position to prevent 

 the viscid matter of the discs of the remaining pollinia 

 from being exposed to the air. 



The Orchis pyramidalis is 

 considered by Mr. Darwin to 

 be the most highly organized 

 species of the British Orchids 

 he has examined. It has 

 sharp leaves, and a close 

 pyramid of white or rose- 

 coloured blossoms. The up- 

 per sepal and the two upper 

 petals form a hood, protecting 

 the anther and stigmatic sur- 

 faces from the weather. In 

 fig. 77, a front view of a 

 blossom, these are cut off as 

 well as in fig. 78 a, which re- 

 presents a side view of the 

 same blossom 1 deprived of half the labellum, and the 

 upper part of the nectary, or spur. The labellum is long, 



Fig. 77. Orchis pyramidalis : Front 

 view of flower with upper sepal and 

 petals removed ; a, anther; *, stigma ; 

 r, rostellum; I, labellum. 



