Cross-Fertilization of Flowers by Insects. 253 



that in many cases where this adaptation to insects seems so 

 perfect the insect visitors aid in securing self-fertilization, as 

 these observations seem to indicate. 



III. Peculiar position of stamens and pistils. — In the pre- 

 ceding paragraph I have already briefly referred to the flowers 

 of Kahnia latifolia, perhaps the best illustration of such an 

 arrangement. The wheel-shaped corolla, with the ten 

 pockets in which the anthers are held, is sufficiently familiar 

 to require no further description. Stamens and pistil mature 

 at the same time. The anthers are held in the pockets of 

 the corolla ; when visited by insects they are set free, and the 

 pollen is thrown with considerable force from the anther-sacs 

 through the orifices. As I have remarked before, I have 

 observed repeatedly that pollen was thrown upon the stigma 

 of the same flower. Careful observations should decide the 

 question how far in such cases, where there is such a pecu- 

 liar arrangement in the position of stamens and pistils in 

 regard to each other, close-fertilization is possible. 



Even should it be impossible in any case that autogamy, 

 or close-fertilization, is effected, it must be remembered that 

 whenever a plant bears many or clusters of flowers the chances 

 of cross-fertilization are reduced. Insects in such cases may 

 visit many flowers of the same plant ; but this is not cross- 

 fertilization in Darwin's sense of the term. 



IV. Dichogamy j or difference in the time of maturity of 

 stamens arid pistils. — This appears to me the most suggestive 

 and interesting phase of this intricate problem. From a 

 teleological point of view, i. e. if we look for a purpose, we 

 must agree with Darwin and his followers that this is one of 

 the most remarkable adaptations favouring cross-fertilization. 

 Modern science insists, however, that we must use inductive 

 methods, and it is the tendency of the present day to search 

 rather for the causes than for an underlying purpose. If, on 

 the one hand, we affirm that every organ is modified to serve 

 some particular use, we cannot believe, on the other hand, 

 that such modifications are directly due to external factors 

 over which the plant has no control. I am aware that the 

 principle of natural selection may find its application in the 

 most subtle cases ; at the same time it requires, in this parti- 

 cular instance, a considerable strain to make it fit. In 

 reference to dichogamy, Mr. Meehan says positively that the 

 difference between the time of maturity of stamen and pistil 

 is caused by varying degrees of temperature, and that dicho- 

 gamy has its origin in this circumstance, " that whatever its 

 significance, it arises from no effort innate to the plant itself, 

 but from an outside force that can have but little interest in 



