256 THE STRUCTURE OF FLOWERS. 



what more towards the top of the skull-like end of the style 

 than in the small-flowered, one (6). When the skull-like knob 

 in the two forms is pressed against the lower petal, in the 

 large-flowered form the opening of the stigmatic cavity is 

 directed outwards, so that the pollen-grains which have 

 fallen out of the anther-cone can never spontaneously fall 

 into the stigmatic cavity, and must be carried there by 

 insects ; whereas in the small-flowered form the opening of 

 the stigmatic cavity is directed inwards, so that pollen-grains 

 falling out of the anther-cone spontaneously, fall directly 

 into the stigmatic cavity. 



"In the large-flowered form, the opening of the stigmatic 

 cavity (st) bears, on its lower side, a labiate appendage (I) 

 provided with stigmatic papillae, so that a proboscis inserted 

 into the flower when charged with pollen from a previously 

 visited flower, rubs off this pollen on to the stigmatic lip, 

 thus regularly effecting cross-fertilisation ; whereas, when 

 withdrawn out of the flower, charged with pollen, the 

 proboscis presses the lip (Z) against the stigmatic opening 

 (st), thus preventing self-fertilisation. This nice adaptation 

 to those visitors provided with a long proboscis (Lepidoptera, 

 Apidse, Rhingia) is completely wanting in the small-flowered 

 form (b). 



" In the large-flowered form, there is a black wedge-shaped 

 streak (g) on the front of the style, to which Mr. A. W. 

 Bennett first called attention, and which he has interpreted 

 as a guide-mark for those visitors which are diminutive 

 enough to crawl entirely into the flower. This streak is 

 also wanting in the small-flowered form. 



" In the large-flowered form, pollen-grains do not spon- 

 taneously fall out of the anther-cone before the flower has 

 been fully developed for several days ; whereas, in the small- 

 flowered form, in bb far the majority of cases, a great number 



