19:23] Garden Pea and White Sweet Clover 77 



Workers began to turn their attention to the treatment of hard 

 seeds about 1890. Kuntz and Huss used sand paper as a scratching 

 machine. Other investigators have used various forms of sand 

 paper seratchers. In the past ten years most investigators have used 

 some moditication of throwing or blowing seeds against sharp points 

 or needles as a means of puncturing the seed coat. Carruthers, (2) 

 1911, was able to guarantee 98-100 per cent germination of clover 

 seed with a machine of this type. Rose, (14) in 1915, explains a 

 device where seeds are blown against a pad of needles, which very 

 effectively improves germination. Prof. Hughes of Iowa State Col- 

 lege has invented a similar but less complicated machine which is 

 fairly satisfactory and is in use by some seedsmen. 



Harrington, (8) 1915, shows the effectiveness of clover hullers 

 as scratching machines. He finds that while hand hulled white 

 sweet clover has 98 per cent of hard seeds, machine hulled has only 

 20 per cent of hard seeds. Hulling, however, injures some of the 

 seed when set to get the maximum scratching results. 



Hot water treatment has been recommended for a number of years. 

 Jarzymowski, in 1905, used it with some success with legume seeds. 

 Bolley, (1) in 1910, reports success with hot water provided the 

 treatment Avas not so long as to injure the embryo. 



Chemical treatments are receiving more and more attention. 

 Rostrup, (15) in 1896, treats Lathyrus sylvestris seeds for one minute 

 in sulphuric acid and had 100 per cent germination. Bolley (1) has 

 used sulphuric similar to the way it is used by Love and Leighty, (11) 

 in 1912, who treated seed for 10 to 30 minutes to get maximum re- 

 sults. Periods of more than one hour usually injure the seed. 



Many other chemicals have been used ; however, the lower alcohols 

 seem to be most effective. Verschoffelts thinks the water will not 

 wet the cell walls, but alcohol can do this more easily. After the 

 walls are wet they can absorb water. Coe and Martin (3) find that 

 the alcohol treatment is not effective with white sweet clover. 



Several explanations have been offered for dormancy or poor germi- 

 nation of seeds. Crocker, (4 and 5) in 1916, gives a representative 

 list of probable causes. He attributes dormancy in many cases to 

 the hard seed coat, which keeps out water and possibly oxygen. The 

 impermeable portion may be the cutin or the light line. Coe and 

 Martin (3) show by staining whole seeds that the light line is un- 

 doubtedly the limiting factor of absorption, since the stain enters 



