HISTORICAL DEVELOPMENT OF FLOWER POLLINATION 7 



is available for pollination. Meanwhile, however, the stigma is in a place remote 

 from the anthers, and it is still small and closed. Accordingly the pollen of the 

 anthers can hardly, either by mechanical means or by an insect, be brought to 

 the stigma, which does not yet exist. This condition endures for a definite time. 

 After expiry of this, when the anthers have no more pollen, various changes in the 

 filaments come about, and the result of these is that the anthers no longer occupy 

 the place which they previously had. Meanwhile the pistil has so changed that 

 the stigma is now exactly at the place where the anthers were at first ; and as 

 it opens, or the parts which compose it spread out, it takes almost exactly the 

 position which the anthers formerly occupied. But it cannot now receive any pollen 

 from the anthers, for they have none left. However, the point where at first the 

 opening anthers and afterwards the opening stigma is found is so chosen in every 

 plant that the insect for which the flower is adapted can only reach the nectar 

 when it simultaneously touches the anthers of the younger flower, or the stigma 

 of the older, with the same part of its body, thus removing pollen from the former 

 and bringing it to the latter, and so pollinating the older flower with the pollen 

 of the yoimger. These dichogamous hermaphrodite flowers are accordingly, so 

 far as fertilization is concerned, like flowers with sexes half separated. At first 

 they are male and afterwards female. ... It never occurred to me whether the 

 opposite of this arrangement might be found in Nature, whether there might be 

 flowers whose stigmas ripened first, and whose stamens only began to mature after 

 fertilization of the carpels. Though it was natural to come upon this idea, yet 

 it did not occur to me till Nature itself brought me to it; and this occurred when 

 I investigated Euphorbia Cyparissias. I saw there that as soon as a flower opens 

 the stigmas first of all come forth, stand quite erect, and spread out. After a few 

 days the whole pistil, which is upon a little stalk of its own, projects quite out 

 of the flower, gradually losing the erect position, and finally turning its stigmas 

 towards the earth. Only then do the stamens make their appearance one by one 

 and the anthers take the same position which the stigmas formerly had.' Conse- 

 quently if insects ' visit an older flower, they must necessarily carry off" pollen from 

 the anthers; and in order that they may do this unhindered, the pistil has left 

 its former position and turned towards the earth. If the insects next visit a younger 

 flower, they must poUinate the stigmas by touching them with their pollen-covered 

 bodies, and so fertilize the younger flower with the pollen of the older.' 



'As there are two kinds of dichogamy, they must be distinguished from one 

 another by diff'erent names. The first discovered I call the male-female [we now 

 say protandrous], and the later discovered the female-male [protogynous] dichogamy 

 (dichogamia androgyne, dichogamia gynandra). The opposite of dichogamy is 

 called homogamy.' 



In contrast to nectar flowers, which are pollinated by the agency of insects, 

 are flowers pollinated ' in a mechanical way by the wind.' These, the wind flowers 

 as we now call them, produce a much greater quantity of pollen than the insect 

 flowers. In the former there must be far more pollen than is required for fertiliza- 

 tion, 'for the wind does not always blow it exactly towards the female tree, and 

 moreover, does not bring every pollen-grain to a flower that has not been fertilized. 

 Again, the rain not only washes much pollen from the anthers, but carries down 



