180 YEARBOOK OF THE U. S. DEPARTMENT OF AGRICULTURE. 



tests only fine-looking seeds are used. These would, of course, give 

 a higher percentage of germination than could be sustained by the 

 entire sample. In selecting grass seeds for testing, care must be taken 

 to use only such as contain a grain. In some kinds of grass seeds 

 there are many empty glumes which it is difficult to distinguish from 

 those containing a grain. A simple way to separate them is to wet 

 the seed, spread it out on a plate of glass, and hold the plate up to 

 the light. The empty chaif will appear translucent, while the good 

 seed will be opaque. 



KEEPING A RECORD. 



Although for the results usually desired in home seed testing it is 

 not absolutely necessary to keep a record, yet such a record, if well 

 made, will be found to contain much valuable information. A few 

 items will always need to be recorded, in any event, such as the date 

 of beginning the test, the name of the variety, the number of seeds, 

 and the number of germinated seeds removed from day to day. It is 

 dangerous to trust anything to memory. Mistakes are sure to occur, 

 and the test will then be useless. 



LENGTH OF TIME REQUIRED. 



The length of time a -test should continue depends upon the seed. 

 In the seed-control stations ten days has been accepted as the proper 

 time for most seeds, but a few require a longer period, namely: 



Days. 



Esparsette, serradella, beet-seed balls, rye grasses, timothy, carrots 14 



Grasses, except meadow and rye grasses, and timothy 21 



Meadow grasses (Poa) , coniferse (except white pine), birches, alders, acorns, 



beeches, and hornbeams _ _ _ 28 



White pine and stone fruits 42 



The seeds should be examined each day, and those that have ger- 

 minated should be removed and the number recorded. A seed is con- 

 sidered as germinated as soon as the root breaks through the seed 

 coats. 



Under favorable conditions more than one-half of the seeds in a 

 good sample will germinate in a much shorter time than that given 

 above. The rapidity with which the seeds germinate is some indica- 

 tion of the vigor of the embryo, and determines the germinative 

 energy. 



The number of days in which more than one-half of the seeds in a 

 good sample should germinate has been fixed as follows: 



Days. 



Cereals, clovers, peas, vetches, flat peas, flax, dodder, poppy, cabbage, radish, 

 spurry, chicory _ _ 3 



Squashes and pumpkins, cucumbers, beans, spinach, lupine, buckwheat, bur- 

 net _ 4 



Beet, timothy, serradella, bird's-f oot clover, rye grasses, meadow foxtail, reed 

 grass .--,-, r ... r ,...,. r ... T ..,.., r . . . , , 



