442 RELATION TO ENVIRONMENT. 



for pollination before the anthers of the same flower are ripe, are proter- 

 ogynons. 



852. Now if we observe the spadix of another plant we may see a condi- 

 tion of things similar to that shown in fii^. 460. In the tlowrrs in the upper 

 part of the spadix here the anthers are wedgini^ their \va\' through Vietween 

 Ihe armordike plates formed by the sepals, while the -tyiis of the same 

 flowers are still beneath, and the stigmas are not ready for pollination. Such 

 fliiwers are proif?'ondroiis, that is. the anthers are ripe before the stigmas of 

 the same flowers are readv for pollination. In this spadix the upper flowers 

 are proterandrous, while the lower ones are prolerwgynous. so that it might 

 happen here that the lower flowers would be ] ollinaled by the pollen falling 

 on them from the stamens of the upper flowers. This would be cross pol- 

 lination so far as the flowers are concerned, but not so far as the plants are 

 concerned. In some individuals, however, we find all the flowers proter- 

 androus. 



863 Spiders have discovered this curious relation of the flowers and in- 

 sects. — < )n several different occasions, while studying the adaptations of the- 

 flowers of the skunk's cabbage for cross pollination, I was interested to find 

 that the spiders long ago had discovered something of the kind, f(.)r tne_y 

 spread their nets here to catth the unwary but useful insects. I have not 

 seen the net spread over the opeinng in tlie spathe, but it is spreail over th.e 

 spadix within, reaching from tip to tip of either the stigmas, or stamens, or 

 both. Behind the spadix crouches the spider-trapper. The insect crawls 

 over the edge of the spadix, and plunges unsuspectingly into the dimly 

 lighted chamber below, where it becomes entangled in the meshes of the 

 net. 



Flowers in which the ripening of the anthers and maturing of the stigmas 

 occur at difierent times are also said to be dickogajnous. 



854. Pollination of jack-in-thepulpit. — The jack-in-thc pulpit (Arispema 

 triphyllum- has made greater advance in the art of tntorcing cross pollina- 

 tion. The larger lumilier of phmts here are, as we have found, diceciiins. the 

 staniinate flowers being on the spadix ut one plant, while the ]:)istillate flowers 

 are on the spadix of another. In a few plants, however, we find both 

 female and male flowers on the same spadix. 



855 The pretty bellflower (Campanula rotundifoUa) is dichogamous 

 and proterandrous (fig. 462). Many of the composites are also dichoga- 

 mous. 



856. Pollination of orchids. — But some of the most marvellous adaptations 

 for cross pollination by insects are found in die orchids, or members of the 

 orchis family. The larger number of the mendiers o'[ this familv grow in the 

 trojtics. Many of tlie^e in ihe forests are su]i]iorted in lofty trees where the) 

 arc l)rouglit near the sunliL^lit. \\\\'\ snrh are called " ejiiphylcs," A numbei 

 of S[)ecies of orchids are dislnhnled ,a ((anpirate regions. 



