3 o8 



BOTANICAL GAZETTE 



[OCTOBER 



This series of experiments shows that the imbibition and osmotic 

 forces alone cause an average elongation of about 20 per cent in 



the embryos partly freed from the coat. The elonga- 

 tion all occurs within 2 . 5 hours when the temperature 

 is maintained at 25 C. This elongation of the embryo 

 is probably three to five times that taking place when 

 the intact seed is soaked for the same time or even for 

 months. It is probable that the swelling of the embryo . 

 in thickness is inhibited to quite as large a percentage 

 by the coat, for when one observes the embryo pro- 

 truding from the coat, owing to the removal of the 



at either end, he sees a marked constriction at 



the line of the broken edge of 



elongation 



coat. The much swollen 

 acellular layer seems to restrict 

 greatly the swelling of the por- 

 tion of the embryo within it. 

 Growth begins within five 



hours on 



average 



when 



partly naked embryos are 



placed 



water 



25 



c. 



Even 16 hours in water at this 



• // 



Time 



16 h 



21 h 



41 h 



Fig. 7. — Percentage of elongation of 14 Alisma embryos with seed coats removed 

 at both ends, soaked 16 hours in water, then placed in 2 mol. cane sugar solution for 

 25 hours: i, curve for the 14 embryos studied; i', curve for the embryo showing the 

 greatest swelling; i", curve for the embryo showing least swelling. 



temperature shows rather slight growth, although the average 

 elongation is about 36 per cent. This all emphasizes 



the main 



imbibition 



