RADISHES 395 



Seed. For use either in the field or in the forcing house, none 

 but the largest and heaviest radish seed should be used. Seeds 

 which are less than 2 mm. (fa inch) in diameter should be rejected. 

 In commercial seed about one third of the total bulk is below this 

 size. The separation of the large from the small seed can be ac- 

 complished by a screen, with perforations of the desired size, or, 

 on a large scale, by a shaking device which will determine the 

 specific gravity of the seeds by the motion given the apparatus, the 

 large and heavy seeds being sent in one direction and the light 

 ones in another, and the two sizes being caught in different recep- 

 tacles. The advantage of the large seed is that it gives the strongest 

 and quickest maturing plants. It is especially desirable in forcing 

 radishes to have the entire crop mature at one time, and this is 

 also of considerable importance in field culture. Strong plants from 

 large seeds will mature in from 21 to 35 days, while plants from 

 smaller seeds will require from 

 8 to 15 days longer to come 

 to maturity, and plants from 

 very small seeds will never 

 reach commercial sizes. It is 

 therefore economical both in 



, ^, FIG. 147. Marker for sowing seeds 



time and space to separate the , 



in greenhouse 



large seed from the small. 



Seed sowing. Seed sowing can be accomplished in the open, 

 either by the hand drill or by scattering the seed from the hand 

 along the row. Ordinarily, in the field the seed should be planted 

 about | inch deep at the rate of from 30 to 40 seeds to the foot. 

 In order to insure quick germination the earth covering the seed 

 should be firmed so as to bring it into close contact with the seed. 

 Modern seed drills are provided with rollers or press wheels, as 

 shown in figure 117, which follow the drills and accomplish this 

 work quite satisfactorily. Where the work is done by hand, as in a 

 greenhouse or hotbed, the drill can be made by a marker shaped 

 like a T, as shown in figure 147, by taking an ordinary lath, plan- 

 ing it down to | inch in width and nailing it to a cleat 2 inches 

 wide. Such a marker may vary from a few inches in length to the 

 width of the bench or bed. After the seed is scattered and the 

 earth placed over it, the work of compacting the soil above the seed 



