296 BULLETIN 312 



Station, and of E. Brown and H. N. Vinall, of the United States Depart- 

 ment of Agriculture, who furnished some seed for certain of the tests. 

 They also wish to acknowledge the kindness of E. T. Coker, of Society 

 Hill, S. C., who made a field test of some treated cotton seed. The pre- 

 liminary tests that led to the use of the method were made in the 

 laboratory of Dr. C. F. Hottes, of the University of Illinois. 



REVIEW OF LITERATURE 



That others have experienced difficulty from hard seed and have devised 

 means of overcoming it, is shown by the following extract from a letter 

 by Professor C. G. Williams, of the Ohio Agricultural Experiment 

 Station : 



" Regarding our trouble in getting clover seed, which we are using for 

 plant-breeding purposes, to germinate, we find a great degree of variation 

 in- this particular with different plants. With some few 80 to 90 per 

 cent of the seed germinates promptly; with others only 5 to 10 per cent. 

 While I do not have any accurate data for you on this subject, I feel 

 reasonably safe in saying that fully three fourths of our plants show 20 

 per cent germination or below. We are getting very good results from 

 rubbing the seed lightly between sheets of a very fine sandpaper. We 

 line a small box with this sandpaper, then rub the seed gently. This 

 is giving us very good germination. This treatment, of course, would 

 be impossible on a large scale." 



Many experiments have been conducted by different investigators in 

 order to determine methods of treatment for hard seed, looking toward 

 increased germination. In such experiments a large number of different 

 chemicals and enzymes have been used with varied success. Immersing 

 the seed in hot water or pricking it with a needle, as well as ; other 

 mechanical treatments, have been used and often have shown in- 

 creased germination. Certain German seed laboratories have used 

 some of these different methods for scratching or breaking the seed 

 coats in order to increase germination. Rostrup 1 was one of the first 

 investigators to use sulfuric acid on hard seed. A sample of Lathy rus 

 sylvestrus was placed in concentrated sulfuric acid for one minute, 

 and then, with an untreated sample of the same, was placed to ger- 

 minate. At the end of 320 days the untreated seed showed a ger- 

 mination of 76 per cent, while the treated seed gave a germination of 

 100 per cent. Rostrup treated a sample of flat pea seed with acid 

 and obtained a germination, at the end of 60 days, of 28 per cent for 

 the untreated seed and 84 per cent for the treated. Red clover seed 



1 See " Literature," page 336, for reference. 



