1914] 



CROCKER &• DA VIS— DEL A YED GERMINA TION 



303 



is to see to what extent the elongation of the embryos in water is 

 a matter of imbibition and osmosis, and to what extent a matter 

 of growth. Embryos with the seed coats removed at both ends 

 were measured and placed in water for various lengths of time and 

 the elongation determined. They were then transferred to plas- 

 molytic agents and the amount of shrinkage determined. Cane 

 sugar was finally chosen as the water-absorbing agent, for it pro- 

 duced permanent shrinkage and showed relatively low toxicity. 

 Embryos which have been soaked in water for 12 hours and then 

 transferred to 2 volume moL cane sugar for 24 hours are still 

 capable of normal growth when transferred to water. On the 

 other hand, lithium chloride, which in saturated solution has great 

 water-absorbing power, proved unsatisfactory both because of its 



1 



toxicity and the variation in results. 



Table VIII shows the average change in length caused in 8 

 embryos by soaking them 2 . 5 hours in water and then transferring 

 them to 2 volume mol. sugar solution for 40 hours. 



TABLE VIII 



Elongation of 8 Alisma embryos soaked 2.5 hours in water, then transferred to 

 lume mol. cane sugar solution. Seed coats removed from both ends of the embryo. 



2 volume mol. cane sugar solution 

 Temperature 25 C. 



Treatment of embryos 



Air dry 



2 . 5 hours in water 





« 

 « 



u 

 u 



" sugar solution . . 



u 

 a 

 u 



u 



U 



u 



u 

 a 

 a 



* • 



• * 



• • 



5 



2 5 

 40 



Extreme individuals 



1. Dry 



2 . 5 hours in water 



4o " * sugar solution 



2. Dry 



2 . 5 hours in water 



2 5 * * sugar solution 



40 « u it u 



Total length of 

 embryos 



814.O 



969-5 

 866.O 



856.O 



840.O 



84c. o 



Average length of 

 embryos 



101.8 



98 

 08 



Percentage of 

 elongation 



121. 2 



19. 1 



I08.2 



6.4 



IO7.O 



5-2 



IOS.O 



3-7 



IO5.O 



37 



Length of embryo 





109 

 139 





27 -5 



III 



19 



96 

 108 





12.5 



2.0 

 2.0 



Two and one-half hours in water gives an elongation of 19 per 

 cent of the air-dry length, while the transfer to the sugar solution 

 shrinks the embryos back to within 3.7 per cent of the air-dry 



