NURSERY PRACTICE FOR PRAIRIE-PLAINS PLANTING 31 



four separate flats; the germination percent is based on the average 

 of the four samples, or such of these as have suffered no known damage. 

 The flats are placed in the germination room, where a range in air 

 temperatures from 60° to 85° F. is maintained, to simulate outdoor 

 conditions. Overhead light is supplied during the day, the lamps to 

 some extent aiding in heating the germination room. 



As soon as germination is evident, the seedlings appearing above 

 the surface are removed with forceps and their number is recorded. 

 Tests are continued from 20 to 90 days depending on rapidity of germ- 

 ination. 



For those species which have a rest period and require stratifica- 

 tion, the flats of seed, properly watered, are placed for 1 to 4 months 

 in one of several cold-storage chambers maintained at temperatures 

 between 41° and 50° F., and then brought into the germination room. 

 Those seeds requiring only mechanical or chemical scarification or 

 water soaking are treated just before sowing. 



CUTTING TESTS 



For seed of the current year's crop, cutting tests are the most 

 feasible and practical method for the nurseryman to determine the 

 probable percent of good seed. The kernels of good seed are firm, 

 white, or creamy in color, and completely fill the seed cavity. On the 

 basis of number of seeds in a very small sample, it is possible to com- 

 pute the number of good seed in an ounce or pound and thus to de- 

 termine the quantity of seed that must be sown per unit of area or 

 per foot of row, under recommended practice, to give approximately 

 the desired stand. If the seed is several years old, the cutting test 

 must be discounted considerably, and it may be impossible by this 

 method to determine whether or not the seed contains life. This will 

 depend on species, storage method, and general history of the seed. 



TESTS OF EXCISED EMBRYOS 



A rather recent development in seed-testing technique (11) consists 

 in carefully removing the embryo from the seed coat and placing it on 

 moist filter paper at 70° to 75° F. The viable embryo swells or par- 

 tially germinates within 5 to 10 days and shows considerable color 

 change. The dead embryo rots. Results show that no matter how 

 dormant a seed may be, the healthy excised embryo usually shows 

 some swelling and color change within a week's time. 



The technique used depends on the type of seed coat. Hard- 

 coated species such as plum, peach, hawthorn, and chokecherry are 

 cracked with a special tool designed for this purpose. A Nebraska 

 nurseryman has devised a pair of pliers equipped with an adjustable 

 stop screw which works satisfactorily on many species. A small 

 vise has also been used successfully. The hard coat is carefully 

 cracked and the seed is placed in water overnight to soften the inner 

 coat, which is then removed with the aid of a needle. Species such 

 as apple and pear are soaked in water overnight and then the outer 

 and inner coats are removed. Pine and fir seed are soaked in water. 

 the outer coat is removed, and slits are made in the endosperm, which 

 is again soaked in water before removing the inner coat. 



Great care must be taken not to crush the seed or injure the embryo. 

 Injured embryos do not react normally and are susceptible to mold or 

 rot. 



