124 NEOTTE^. Chap. IV. 



tion of the pollinia, so here the rostellum moves back- 

 wards, and not only recovers its former arched position, 

 but stands upright, leaving the stigmatic surface, now 

 rendered more adhesive, perfectly free for pollen to be 

 left on it. The pollen-masses, when once cemented to 

 an insect's forehead, will remain attached to it, until 

 they are brought into contact with the stigma of a 

 mature flower ; and then these encumbrances will be 

 removed, by the rupturing of the weak elastic threads 

 which tie the grains together ; the flower being at the 

 sanie time fertilised. 



lAstera cordata. — Professor Dickie of Aberdeen was 

 so kind as to send me, but rather too late in the 

 season, two sets of specimens. The flowers have essen- 

 tially the same structure as in the last species. The 

 loculi of the rostellum are very distinct. Two or three 

 little hairy points project from the middle of the crest 

 of the rostellum ; but I do not know whether these 

 have any functional importance. The labellum has 

 two basal lobes (of which vestiges may be seen in 

 L. ovata) which curve up on each side ; and these 

 would compel an insect to approach the rostellum 

 straight in front. In two of the flowers the pollinia 

 were firmly cemented to the crest of the rostellum ; 

 but in almost all the others the pollinia had been 

 previously removed by insects. 



In the following year Professor Dickie observed the 

 flowers on living plants, and he informs me that, when 

 the pollen is mature, the crest of the rostellum is 

 directed towards the labellum, and that, as soon as 

 touched, the viscid matter explodes, the poUinia becom- 

 ing attached to the touching object ; after the explosion, 

 the rostellum bends downwards, thus protecting the 

 virgin stigmatic surface ; subsequently it rises up and 

 exposes the stigma ; so that here everything goes on 



