l^'i2j Goodspeed: Nicotiana Hyhrids 131 



4. Sowing of the Seed 



The sowing of the seed is usually commenced during the lat- 

 ter part of March. Pots, 8 inches in diameter and 2^^ inches 

 deep, have been especially provided. They are filled with a 

 mixture of sand and garden soil and sterilized in the autoclav 

 for three hours, at eighteen to twenty pounds pressure. For 

 each pot cheese-cloth covers suitably cut are sterilized at the 

 same time. When the pots come from the autoclav these cover- 

 ings go on at once and are secured by wire rings about the pots. 



Two persons also are needed in sowing the seed. Two sizes 

 of clean paper are again laid upon the table and the covered 

 pot placed upon them. The bookkeeper gives the first package 

 of clean seed to the "sower" and, lifting the covering off the 

 pot, lays it on the white paper always with the side that has 

 been nearest the soil uppermost. The sower then opens the 

 outer seed envelope, unwraps the paper, and compares the label 

 with the designations on the two envelopes. If no mistake has 

 been made and the three agree, the sower reads the seed numbe^' 

 from the label and it is checked off on the bookkeeper's list. 

 The sower now tears open the seed envelope proper and shakes 

 out the seed rather thickly over the surface of the soil. Any 

 seed remaining is wrapped up again and laid aside. Granite 

 pans, one for each pot and previously sterilized in the flame, are 

 used to press down the seed into the earth. The bookkeeper 

 now returns the cloth covering, secures it and writes the proper 

 designation on the side of the pot. The two papers and the 

 pan for pressing down the seed are now discarded, the sower 

 washes his hands and the whole operation is repeated. 



Since this paper constitutes one of the first of a considerable 

 series on breeding investigations in Nicotiana which will prol> 

 ably be published from this laboratory, under Professor Setch- 

 ell's direction, it has seemed necessary in the above to go with 

 some detail into the technique he has adopted, which holds rigidly 

 for this particular experiment and in general method for all other 

 allied investigations in the Botanical Garden of the University 

 of California. 



