3io 



BOTANICAL GAZETTE 



[OCTOBER 



5. Elasticity of the seed coat. 



attempt was made 



determine the elasticity of the seed coat of Alisma. Thirteen 

 good seeds freed from the ovary wall were selected and the length 

 measured from the crown of the arch to the tip of the big arm and 

 the width across the middle of the two arms. The seeds were 



remeasured and placed in 2 mol 



measured 



d 24 hours. They were 

 measured : then followed 



in dry air -with the final measurement. Table XIII 

 modifications brought about in the two dimensions by 

 5 treatments. The slight 



shrinkage 



fer from water to cane sugar is especially noticeable. It shows the 

 very slight elasticity of the seed coat as compared with the embryo. 

 The total elongation of the intact seed, which is reached after two 



becomes no greater even after mon 

 as compared with the embryo (19 ] 



5 



. TABLE XIII 



Thirteen Alisma seeds, ovary wall removed, seed coats intact, soaked in water, 

 followed by 2 volume mol. sugar solution, followed by water, and finally dried in 

 air to get an estimate of the elasticity of the coats. Temperature 25° C. 



Treatment or the seeds 



Air dry 



1 day in water 



15 hours in sugar solution 

 24 « " « « 



1 day " water 



4 days a air 



Width in scale 



LENGTHS 



Total 



334.0 



494 .0 

 481.0 



478.0 



S08.0 



447-5 



Average 



25.7 

 38.O 



37-0 

 36.8 



39-6 

 34-4 



Length in scale 



LENGTHS 



Total 



905 

 993 

 963 

 952 

 996 



931 



8 



5 

 o 



5 

 o 



Average 



69.7 

 76.4 



74.1 

 73-2 



76.6 

 71.6 



Percentage of 

 increase over dry size 



In width 



14.0 

 11. o 



10. o 

 17.0 



3° 



In length 



9.8 

 6.3 



5-3 

 10. o 



3-° 



6. UXYGEN PRESSURE IN RELATION TO THE GROWTH OF ALISM 



seeds and seedlings.— We have already shown that the failure 

 of Alisma- embryos to break the coats, as well as their dormancy 

 is due to the fact that their possible imbibitional and osmotic 

 swelling can be only in small part consummated in the intact seed. 



(N. 



I 



876) that the 



me 



mechanical 



on 



