294 



BOTANICAL GAZETTE 



[OCTOBER 



experiments may be explained in part by the difference in tempera- 

 ture. When Fischer used 0.2 or 0.3 N HC1 with one or two 

 hours' exposure as a forcing agent, he found 40 C. a very effective 

 temperature. Individual seeds also show great variation in the 

 readiness with which they swell to the maximum and begin growth. 

 Old seeds, such as those used in the experiments with CuS0 4 , 

 seem more resistant to HC1. This is prominent even in cases 

 where the coats are broken, as later results will show. 



The curves for the absorption of water with the coats broken 

 correspond closely in the two experiments reported, as they do in 

 all the experiments. In these seeds the absorption of water is very 

 rapid during the first 2-4 hours, amounting to 65-80 per cent of the 



TABLE II 



Showing percentage absorption of water (figured on the basis of air-dry weight) 

 by Alisma seeds: I, coats broken, seeds in water; II, coats intact, seeds in water; 

 III, coats intact, seeds 2 hours in o. 2 N HC1 and then in water. Temperature 25 C. 



No. of hours soaked 



I 



2 



6 



9 

 21 



52 



Percentage of water absorbed on basis of air-dry weight 



I 



32 



55 

 80 



80 



101 



160 



•5 



II 



23 

 33 

 45 

 45 

 5i 

 5i 



III 



45 

 52 



53 

 61 



73 

 96 



air-dry weight, or to approximately 100 per cent of the dry w< 

 This is followed by a period of 10 or more hours of very 



absorption, which 



tion. 



matter 



of imbibition and osmosis. The slow water absorption lying 

 between these marks the interval between imbibitional and growth 

 enlargement. 



With the untreated intact seeds the water absorption essentially 

 all occurs within 2-4 hours, and approximates 45 per cent of air- 

 dry weight, or about 70 per cent of dry weight. The imbibitional 



osmotic 



mbry 



nearly satisfied, for, as is shown above, when the coat is broken 



