166 VANDE^. Chap. VI. 



nectary had been acqiured by successive modifications. 

 As certain moths of Madagascar became larger through 

 natural selection in relation to their general conditions 

 of life, either in the larval or mature state, or as the 

 Droboscis alone was lenfrthcned to obtain honev from 

 the Angraecum and other deep tubular flowers, those 

 individual plants of the Angrsecum which had the 

 longest nectaries (and the nectary varies much in 

 length in some Orchids), and which, consequently, 

 compelled the moths to insert their proboscides up to 

 the very base, would be best fertilised. These plants 

 would yield most ssed, and the seedlings would 

 generally inherit long nectaries; and so it would be 

 in successive generations of the plant and of the moth. 

 Thus it would appear that there has been a race in 

 gaining length between the nectary of the Angraecum 

 and the proboscis of certain moths ; but the Angrajcnm 

 has trimnphed, for it flourishes and abounds in the 

 forests of Madagascar, and still troubles each moth 

 to insert its proboscis as deeply as possible in order to 

 drain the last drop of nectar. 



I could add descriptions of many other curious 

 structures in the Vandeae, more especially from the 

 letters of Fritz Miiller with respect to those of Brazil ; 

 but the reader would be w^earied. I must, however, 

 make a few remarks on certain genera, the fertilisation 

 of which remains a mystery, chiefly on account of the 

 narrowness of the mouth of the stigma, as this renders 

 the insertion of the pollen-masses extremely difficult. 

 Two closely allied species or varieties of Acropera, viz., 

 A. luteola and loddigesii have been observed by me 

 during several seasons, and every detail of their struc- 

 ture seems as if specially adapted to render their 

 fertilisation almost impossible. I have met with hardly 



