ae 
THE NATURAL HISTORY OF THE FLOWER. 289 
one on each side of it. The smooth grooves lead them up to the 
stigmatic slit in the most exact manner possible; but we find 
that they are too broad to enter. This is the chief difficulty that 
Darwin found in Stanhopea oculata : it has also been noticed by 
other writers. The author has unfortunately not had an oppor- 
tunity of examining this species. In it, according to Darwin, 
the pollinia do not shrink on drying; but in the species under 
consideration they do shrink considerably. The slit (fig. 9) in 
the pollinium narrows by the moving together of its sides, and 
the width of the pollinium is thus reduced sufficiently to enable it 
to enter the stigma. This process takes from 12 to 24 hours, 
according to the dryness of the air. The delay thus caused will 
ensure cross-fertilization. Ifthe experiment with the pencil be 
tried after this period, it is beautiful to see the manner in which 
the pollinia slide up to and into the stigma. As one moves the 
pencil on, the caudicles are stretched at right angles to the 
pollinia and presently break, leaving the latter buried in the 
stigmatic slit. Withina day or two the pollinia are sucked right 
into the cavity out of sight, and a sticky fluid exudes from the 
mouth. 
The flower was found by experiment to be self-fertile (in 
Cambridge). Flowers fertilized from another plant set good 
seed, even when the pollinia were a week old. The flower itself 
lasts only three days, even when not fertilized, a somewhat 
unusual circumstance in these large and showy orchids. 
We come now, finally, to the mode in which insects are attracted 
to the flower, and the way in which it is actually fertilized in 
nature. Unfortunately, as has already been explained, it has 
not been possible to study the plant in its native place; so that 
this part of the work must remain doubtful. The flower is 
very conspicuous from the side or from below, and possesses a 
very powerful vanilla-like odour, which gives a headache to a 
person sitting over it for any time, and renders our British bees 
almost incapable of walking if they are shut in with the flower 
fora couple of hours. The cage formed by the column and 
labellum hangs downwards, as already explained; and is extremely 
slippery inside and out except in a few spots, viz. the stalk 
portion of the column, the interior of the bucket (the slipperiness 
begins at the mouth of the bucket), and the back of the same. 
It was found, by experiments with hive- and humble-bees, that 
they were unable to climb up the slippery labellum. 
This fact, taken together with the pendulous position of the 
