128 



pistils are so arranged that self-pollination can take place 

 readily, seed did not set unless pollen was brought from 

 another plant. 



Gaertner was unable to self-fertilize Lobelia fulgens, 

 although fertile seeds were produced when the pollen of 

 other species was used. The same state was found to exist 

 in Veibascum nigrum, and according to Tinzmann in the 

 potato {Salanum tuberosum). 



Darwin, 11 Fritz Mueller and others, made observations 

 to show that the pollen has no effect unless it comes from a 

 different plant. It has been shown that the pollen from 

 another flower of the same plant ia scarcely more potent 

 than pollen from the same flower. Now, the greater differ- 

 ence in the individual, the greater the potency. In some 

 cases the potency is greater from a different variety. Fritz 

 Mueller has made the interesting observation that in some 

 plants when the pollen is placed on the stigma of the same 

 flower, it has no more eff'ect than. dust. In other cases when 

 the pollen of the same flower was placed on the stigma, it 

 acted on it like poison. The flower faded and fell oft. 

 Flowers not so treated on the same branch remained fresh. 

 Darwin has shown that in plants known as heterostyled the 

 number of seed produced in illegitimate unions was small 

 indeed and full fertility only resulted when the pollen from 

 stamens was brought to styles of the same length. 



It is well know that in Australia there was much diflicul- 

 ty in getting clover to seed until the introduction - of the 

 bumble bee. Experiments^^ have been made in this country 

 as well as Europe to show that clover mast be cross-pollin- 



11 Different forms of flowers. CroBS-feBtilizatiou, p. 219. 



12 Darwin, oross-fertilization, p. 261, etc., etc. 

 Sirrine: Bull, 13, Iowa Agrl. Kxp. Sta. 



