Hulled seed usually germinates much better than unhulled seed, as is shown in Table I.
Table I.—Germination and hard seed content of samples of sweet-clover seed, hulled, and unhulled, from different sources.
| Description. | Number of samples. | Average percentage of— | |
| Germination. | Hard Seed. | ||
| Kind of seed: | |||
| Hulled | 237 | 53.25 | 18.7 |
| Unhulled | 45 | 11.8 | 70.9 |
| Source of seed: | |||
| Southern | 22 | 14 | 60 |
| Northern | 22 | 37 | 43 |
| Imported | 28 | 56 | 12 |
Table I shows that northern-grown seed germinates better than northern-grown seed and imported seed better than either. The low germination of the southern-grown seed is probably due to the fact that a very large percentage of it is flailed out and sown in the hull. Northern-grown seed generally is thrashed with either a grain separator or a clover huller. Imported seed always is hulled. In hulling seed the rasps or concaves of the machines scratch the seed coats sufficiently to permit water to penetrate them, so that the germination is greatly increased. Apparently there is no reason why southern-grown seed when it is properly hulled should not germinate as well as northern-grown seed.
Since the Ames scarifying machine ([fig. 8])[7] has been placed on the market, it is possible to buy scarified seed. This machine is so constructed that the seed is forced through a conveyor, part of which is covered with sandpaper. When the seed comes in contact with the sandpaper it is scratched, so that water will penetrate the seed coats. When this machine is run properly the germination of seed is greatly increased, but when carelessly operated germination may be lessened, as many of the seeds may be broken.
[7] This machine was invented by Prof. H. D. Hughes, of the Iowa State College at Ames. A United States patent covering this device has been issued and dedicated to the free use of the public.
Fig. 8.—Ames hulling and scarifying machine.