188 Alfred J. Ewavt : 



longed high temperature, although unswoUen Acacia seeds can 

 be kept a week or more under water at 60 to 65 deg. C. without 

 entirely losing their vitality. Similar results were obtained 

 with Acacia myrtifolia, but in all cases if the seeds were merely 

 soaked for one to two days the t-emaining hard seeds, after filing 

 or treatment with sulphuric acid, always gave a higher percent- 

 age germination than those which had swollen in water pre>- 

 viously. 



Alkali is much less effective than sulphuric acid in producing 

 swelling without injuring the seeds. Thus of old seeds of Acacia 

 dealhata soaked in water at 40 deg. C. for 2 days, 9 per cent, 

 swelled, and of these 2.3 per cent, germinated. After soaking 

 in 5 per cent. Na.^ CO.^ for 1 day at 20 deg. C, and then 1 day at 

 40 deg. C. to 50 deg. C, in waiter, 45 per cent, swelled, and of 

 these 5.2 per cent, germinated. After 1 minute in boiling 10 per 

 cent, caustic soda, 28 per cent, swelled after frequent washing, 

 and 3.4 per cent, of these germinated ; while after 2 minutes in 

 boiling potash, 78 per cent, swelled and 4.6 per cent, germ- 

 inated. After 10 minutes all swelled, but none germinated. 

 Longer treatment with cold caustic soda also produces swelling, 

 but the difficulty of causing all the seeds to swell without injuring 

 all or most of them is equally great. Ammonia is less effective 

 than caustic soda or potash. 



The 10 per cent, caustic soda or potash is useful, however, 

 for seed testing. Thus, if an old sample of seed of Acacia 

 dealhata is boiled for 2 minutes in the solution, washed well 

 aoid sr.aked in water at 40-50 deg. C. for 3 hours or so, all unfilled, 

 perforated or broken, seeds, and most dead seeds, swell up par- 

 tially or entirely, and exude a dark brown dye. All. or the 

 great majority of the sound seeds are still hard and unswollen. 

 Tlie test is not perfect, but will distinguish a good from a bad 

 sample of Acaciai seed. 



The sulphuric acid treatment has this advantage, that the 

 concentrated acid only penetrates slowly even after the cuticle 

 has been dissolved away, and with careful treatment the whole 

 of the .subjacent layers are left intact. Further, it sterilizes the 

 seeds and destroys all adherent spores. In addition germination 

 is usually hastened as compared with seeds which haa-e swelled 

 without treatment. The chief danger lies in allowing traces of 



