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. [Illustration: Fig. 8.--Ames hulling and scarifying machine.] The retarded germination of sweet-clover seed may be overcome by soaking it in commercial concentrated sulphuric acid for 20 minutes. It should then be washed quickly, using running water if possible, as sulphuric acid becomes very hot when mixed with small proportions of water. A great deal of water therefore is necessary in order to lessen the danger of burning. The seed should be dried quickly by spreading it out on a floor or canvas, and it should be stirred at intervals. Unhulled seed should never be treated with sulphuric acid. When only a small quantity of sulphuric acid comes in contact with the hulls a very high temperature will result and the seed will be killed. The treatment of seed with sulphuric acid for seeding on a field scale is not to be recommended, in view of the fact that as good or better results may be obtained by using scarified seed. It is very important that seed of the desired species be obtained. Many lots of sweet-clover seed offered for sale on the market consist of mixtures of the yellow and white species, and many samples also are adulterated with alfalfa. Seed which is simply labeled sweet clover should never be purchased, as seed so labeled may be any one of the several varieties offered for sale. It is always best to state the specific kind of seed ordered and then submit a sample to either your State Agricultural experiment Station or one of the seed laboratories of the United States Department of Agriculture[8] for identification before purchasing. [8] Samples of seed may be submitted for analysis or identification to the Seed Laboratory of the United States Department of Agriculture at Washington, D. C., or to any of the following laboratories maintained through the cooperation of the Department: Branch Seed-Testing Laboratory, Agricultural Experiment Station, Columbia, Mo.; Branch Seed-Testing Laboratory, Agricultural Experiment Station, Baton Rouge, la.; Branch Seed-Testing Laboratory, Oregon Agricultural College, Corvallis, Oreg.; Branch Seed-Testing Laboratory, Purdue University, La Fayette, Ind.; Branch Seed-Testing Laboratory, California Agricultural Station, Berkeley, Cal.