130 HETEROSTYLED DIMORPHIC PLANTS. CHAP. Til 



from the long-styled being quite smooth. Fritz Miiller 

 remarks that this difference between the pollen-grains 

 of the two forms is evidently of service to the plant ; 

 for the grains from the projecting stamens of the short- 

 styled form, if smooth, would have been liable to be 

 blown away by the wind, and would thus have been 

 lost ; but the little points on their surfaces cause them 

 to cohere, and at the same time favour their adhesion 

 to the hairy bodies of insects, which merely brush 

 against the anthers of these stamens whilst visiting 

 the flowers. On the other hand, the smooth grains 

 of the long-styled flowers are safely included within 

 the tube of the corolla, so that they cannot be blown 

 away, but are almost sure to adhere to the proboscis of 

 an entering insect, which is necessarily pressed close 

 against the enclosed anthers. 



It may be remembered that in the long-styled form 

 of Linum perenne each separate stigma rotates on its 

 own axis, when the flower is mature, so as to turn its 

 papillose surface outwards. There can be no doubt 

 that this movement, which is confined to the long- 

 styled form, is effected in order that the proper sur 

 face of the stigma should receive pollen brought by 

 insects from the other form. Now with Faramea, as 

 Fritz Miiller shows, it is the stamens which rotate on 

 their axes in one of the two forms, namely, the short- 

 styled, in order that their pollen should be brushed off 

 by insects and transported to the stigmas of the other 

 form. In the long-styled flowers the anthers of the 

 short enclosed stamens do not rotate on their axes, 

 but dehisce on their inner sides, as is the common 

 rule with the Rubiaceae ; and this is the best position 

 for the adherence of the pollen-grains to the proboscis 

 of an entering insect. Fritz Miiller therefore infers 

 that as the plant became heterostyled, and as the 



