106 SEEDING AND PLANTING 



13. THE TESTING OF TREE SEED 



The external appearance of the seed will determine its genuine- 

 ness, the degree of purity, and whether it is of normal size and color. 

 The internal appearance will determine the percentage of blind, 

 decayed, moldy, rancid, wormy, and dried-out seed. When the 

 kernel fills the seed coat and is firm, moist, sweet-smelling, of good 

 color, and apparently fresh, the seed is most likely good. The 

 impaired vitality resulting from too long storage or from overdry- 

 ing or drying at too high a temperature cannot be safely determined 

 by direct examination. 



A thorough test to determine the quality of tree seed should 

 include the following: 



a. An examination for purity, i.e., freedom from foreign matter. 



b. An examination for genuineness, i.e., whether true to name. 



c. The determination of viability. 



The high cost of most forest tree seed and the expense incurred 

 in nursery practice and direct seeding make it imperative that only 

 good seed be used. 



14. The Determination of Purity 



The percentage of purity of tree seed is determined by weight. 

 A carefully selected sample, which represents the average of the 

 entire lot of seed to be tested, Is weighed. After weighing the 

 sample is spread out on a sheet of white paper and all impurities 

 separated from the seed. The weight of the impurities divided by 

 the weight of the sample gives the percentage of impurities. As 

 yet in this country we have no table of standards of purity for 

 forest tree seed, and there is great variation in the amount of 

 impurities in most species as obtained from dealers. A certain 

 amount of impurities is admissible in all seed. This, however, 

 varies greatly with different species, depending upon the expense 

 involved in separating the seed from such impurities. The purity 

 of all seeds that are easily separated from the fruit and from foreign 

 matter is high, while it is correspondingly low for those that are 

 difficult to separate. The seed of most conifers is easily cleaned 

 and should be practically pure. The seed of some species, how- 

 ever, like the longleaf pine cannot be readily separated from the 

 wings and is relatively impure. Other species, as illustrated in 

 arbor-vitse, have small, light, flat seed which cannot be easily 



