PROPAGATION BY SEEDS 49 



The fact that the seeds sprout, however, does not show that 

 they are sufficiently viable to produce mature plants, but 

 indicates merely that they have not lost all vitality. 



66. Adulterated seed. Sometimes inert material, old 

 seeds, and other seeds resembling those desired are mixed 

 with good seed. Inert material and seeds of different kinds 

 can be detected by examining them with a microscope. Ger- 

 mination tests will reveal the presence of old seed. Sometimes 

 they can be told by their color. 



67. Special methods of causing seeds to germinate. 

 Certain seeds are benefited by special treatment. The value 

 of stratification in softening and cracking hard shells has 

 been mentioned. 



Soaking for a few hours in water to hasten germination is 

 practiced with pear and apple seeds, corn and many vegetable 

 seeds. The soaking should be stopped as soon as the seeds 

 have swollen, and the planting should take place immediately. 



Seeds having hard thick coats may be treated by scalding. 

 Boiling water should be poured over them and allowed to 

 cool. The seeds should remain in the water until they show 

 signs of swelling. Seeds of the canna, certain locusts, a few 

 conifers, and the Kentucky coffee-tree are examples of seed 

 treated in this manner. 



Many seeds with hard coats are benefited by being soaked 

 in acids. Clover and alfalfa seed are soaked in sulfuric acid 

 for a few minutes, and then washed thoroughly in water. 

 When it is necessary in plant-breeding to plant the seeds of 

 the blackberry, raspberry, or dewberry, soaking them a short 

 time in vinegar is advisable. Seeds of the sweet-flag, pond- 

 lily, arrowhead, cat-tail, and many of the sedges are benefited 

 by weak acid treatments. 



Mechanical treatments, such as filing, grinding, or clipping, 

 are practiced on some hard-coated seeds (among which are the 

 wild cucumber, canna, and olive) as an aid to the entrance of 

 water. A portion of the coat is removed down to the embryo. 



