NURSERY PRACTICE FOR PRAIRIE-PLAINS PLANTING 29 



is hinged to allow removal of seed and permit access for relining the 

 drum and disks with abrasive. The abrasive consists of No. 2%, grade 

 30 E. silicon carbide sandpaper, held in place by casein glue. The 

 cylinder is suspended on the shaft in such a manner that the removal 

 of a pin will allow it to be rotated, thus facilitating the removal of the 

 seed. 



This scarifier is run at speeds of 500 to 900 r. p. m. and can handle 

 about 10 pounds of tree seed of any size. Only the lower half of the 

 cylinder is filled with seed. As the seed is scarified, it circulates 

 gradually over the top of the cylinder, so that all seed is given an even 

 treatment regardless of variation in size. For any nursery where 

 large quantities of seed are to be treated, a larger machine can be 

 built in which the wooden disks can be replaced advantageously by 

 solid carborundum grinding wheels. All other parts can be made of 

 metal. 



This type of disk scarifier is much more effective than the revolving 

 drum or box type. A few minutes' treatment is sufficient for thin- 

 coated black locust and similar species. Hard-coated species will 

 require a longer period. The length of time of treatment for a given 

 kind of seed must be worked out by actual test for each size of scarifier. 

 The type of abrasive used will also influence the effectiveness of the 

 treatment. The seed used must be quite free of resin or soft pulp to 

 prevent gumming-up of the abrasive. 



SOAKING IN COLD AND HOT WATER AND OTHER TREATMENTS 



Seed of all species must absorb water before they will germinate. 

 Where scarification or stratification are not practicable, the germina- 

 tion period for many spring-sown seeds, even those having no dor- 

 mant period, can be shortened considerably and a higher and more 

 uniform germination obtained by soaking them in cold water until 

 they swell. This may require as much as 2 weeks in cases where seed- 

 coat dormancy is natural or has been induced by long or severe drying. 

 Nurserymen have reported cases which point to the conclusion that, 

 while soaking in water is not the preferred treatment, practically all 

 deciduous species grown for prairie-plains planting respond to it 

 favorably as an emergency treatment. 



Water in which seed is soaked should be changed every day. other- 

 wise it becomes sourish and has a detrimental effect on seed viability. 

 Better still is to place the seed in burlap sacks and immerse them in 

 running water, as a stream or river, thereby providing both fresh water 

 and aeration. For a number of light seeds, notably elm. catalpa. and 

 desertwillow, water absorption can best be accomplished by placing in 

 wet sand instead of cold water. Soaking, to be most successful, must 

 be continued until the larger portion of the seed swells. The seed 

 should then be sown as soon as possible. 



Hot-water treatment has been used with the larger legume seed as 

 a means of softening the impermeable seed coat, in preference to acid 

 treatment or mechanical scarification. As a general rule, a given volume 

 of these hard-coated legumes can be immersed in an equal volume of 

 boiling water and then allowed to cool, without injury. According 

 to Phillips (30), the water must be just below the boiling point. This 

 is not always effective but probably is as far as one can safely go. 



