28 NATURE STUDY. 



In crawling out through one of the little side openings the 

 insect has first to pass close to the stigma and next close 

 to the anther. We will suppose the visitor to be making 

 his first morning call, and to have as yet no pollen adher- 

 ing to him. He brushes past the stigma, but of course 

 leaves no pollen on it. When he reaches the anther, the 

 delicate membrane which covers the anther cells is rup- 

 tured and some of the pollen, which in this species is vis- 

 cid, sticks to him. Having emerged, he seeks another 

 flower. In making his exit from this he first brushes past 

 the stigma. This is beset with sharp points, all directed 

 forward, which favor the deposit of some of the pollen on 

 it. So flower number one has not only prevented the in- 

 sect from leaving its own pollen on its own stigma, but has 

 also commissioned him to transfer some of the pollen to 

 flower number two. In this way the process of cross-fer- 

 tilization goes on indefinitely at the same time and by the 

 same means that self-fertilization is effectually prevented. 



In the stemless or pink lady-slipper the process is the 

 same, though the development of the lip is quite different. 

 Instead of a free opening in the top there is a closed fissure 

 in front which may be essily forced through from without, 

 but not from within, by reason of the edges being folded 

 inward, so that exit has to be made by the same outlets 

 as in the other species. 



In the flowers of Cyripedium, then, the changes which 

 have taken place in the interest of cross-fertilization are, 

 briefly, these : From a regular flower with three sepals, 

 three petals, three outer stamens, three inner stamens and 

 three pistils there has come a very irregular flower. The 

 three sepals remain, though two of them are often appar- 

 ently united into one ; two of the petals remain as petals, 

 while the third has been changed into the slipper-like or 

 pouch-like lip ; two of the outer stamens have been sup- 

 pressed, while the third has been developed into some- 



