163 



Studies on Pollen. 



F. M. Andrews — Indiana University. 



Since the time of Amici it has been known that pollen grains ger- 

 minate and send out one or two tubes. Amici carried on his studies 

 on this point on the plant Portulaca oleracea. Ever since the work of 

 Amici various investigations have been made on the germination of 

 pollen and especially concerning the different conditions that would 

 promote its growth. Even yet, many points remain obscure and much 

 investigation will be necessary before these are solved. As the chemical 

 nature of the stigmatic fluid is complicated and varies greatly in differ- 

 ent plants, it renders the culture medium used to induce growth a mat- 

 ter of one expe]-iment after another with different media in order to 

 ascertain which will induce growth or is best adapted to the various 

 cases. Of course it is known that in a good many cases a sugar solu- 

 tion will cause growth, but this is by no means the case with the pollen 

 of all plants, so that other means frequently have to be tried. Moreover 

 the physical character of the culture medium is a factor that has been 

 very generally overlooked. 



In the experiments here mentioned I have investigated to date the 

 behavior of the pollen of 435 plants with respect to a culture medium of 

 cane sugar. Of these, 110 showed no response whatsoever as no growth 

 occurred. The remainder showed a more or less pronounced growth. 

 A wide range in the percentage of the cane sugar solutions was used 

 so that ample opportunity for growth was afforded by this medium if 

 such a medium would produce it. Plants from many different families 

 as well as from the same family were tried so as to see in how far 

 differences in germination under such conditions would occur. 



