396 



IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 

 TABLE II. 



PERCENTAGES OF GERMINATION AND LENGTH OF TUBES 



OBTAINED IN DIFFERENT MEDIA IN 16 HOURS AT 



A TEMPERATURE OF 23° C. 



Medium: 



Percentage of Ge:emi- 



NATION AT THE EnD 



OF 16 Hes. 



Approximate Length 

 OF Tubes. 



The average percentage of germination was highest in the 2i/2 

 per cent cane sugar solution. As the concentration increased up 

 to 65 per cent, the per cent of gerinination decreased. A con- 

 centration of 65 per cent was the maximum for germination 

 when the period allowed for germination was no longer than 16 

 hours. However, in some tests, as much as 2 per cent germina- 

 tion was obtained in 72 hours in concentrations of 70 per cent. 



The fact that the pollen germinated to a considerable extent 

 in distilled water suggested that the sugar solutions functioned 

 in the germination of the pollen only in controlling the water 

 supply. Comparative tests run in sugar solutions and on mem- 

 branes (skown in taible III) gave further evidence that this was 



true. 



TABLE III. 



A COMPARISON OF THE PERCENTAGES OF GERMINATION 



OBTAINED IN SUGAR SOLUTIONS WITH THOSE' OBTAINED 



ON MEMBRANES, THE TIME PERIOD BEING 12 HOUKl^. 



Vaueety 



In 2% Cane Sugar 

 Solution. 



On Aniiviai. Membrane 



Wealthy 

 Gano . . . 

 Jonathan 

 Dutchess 



85 

 90 



8:8 



90 



Table III shows that a higher percentage of germination was 

 secured on the membranes than in the sugar solutions. Germi- 

 nation also took place more rapidly and the tubes grew faster 

 and were more nearly normal in appearance on the membranes. 

 In the tubes gro^^Tl in the solutions, there was clumping of the 



