SELF-FERTILIZATION IN TROPICAL ORCHIDS. 543 



there has been going on a slow approximation of the underside 

 of the rostellum to the lower lip of the stigma, the long tongue 

 of the former fitting into the downward-pointed projection of the 

 latter. The lower edges of the stigmatic cavity finally embrace 

 the rostellum, by its lower edges growing over the anther-case, 

 and thereby bending down the whole anther, so that when the 

 act of fertilization has been completed, the stigma is almost 

 obliterated, leaving no room for any foreign pollen to be applied 

 to its surface. The pollen-grains of the tips of the caudicles of 

 the pollinia remain, as a rule, unaffected, but, being not viscid, 

 are not easily removable. The operations here described are 

 invariably far progressed, very often completed, before the opening 

 of the flower. So soon as the pollen-tubes have well penetrated 

 the ovary, the flower begins to fade, the labellum becomes brown, 

 assumes the position it had in the unopened bud, and the sepals 

 and petals slowly wither up and cluster round the column. 



One of the most interesting terrestrial Orchids that I gathered 

 here was a purple variety of the Arundina speciosa, Blume. This 

 cane-like species grows to a height of between 5 and 6 feet, 

 producing without intermission for many months a succession of 

 large and beautiful purple flowers towards the terminal portions 

 of its stems. The labellum is tubular and embraces the column : 

 it has a broad fringed dark purple margin, from which radiate 

 deeper lines converging towards the bright yellow throat, where 

 they merge in two ridges leading to the shallow nectar- depression 

 at the junction of the column and labellum. The open flower 

 stands at an angle of about 60° to the stem, and looks forwards 

 and upwards. The essential organs become so singularly modi- 

 fied that I shall describe them from an early stage in the bud. 



In the very young bud, the column is crowned with a 2-ceIled 

 anther erect on the posterior part of the column by its short 

 filament, Underneath is the stigma, of, roughly speaking, a 

 square shape ; its lateral lower borders forming flap-like projec- 

 tions, while the upper border stands erect in front of the pollinia, 

 rising to about one third of their height as a triangular eminence, 

 the rudiment of the rostellum. It is not in every flower that this 

 can be seen well, for the stage next to be described begins very soon, 

 even before the entire column from its base to the summit of the 

 anther-case has reached barely the height of 4 millimetres ; it is only 

 by the examination of a very large series that I have been able to 

 follow the modifications that have occurred. The anther now 



