In addition to treating seed to kill insects it is sometimes desirable, 

 as in the case of cotton, for instance, to fumigate imported seed to 

 avoid any risk of the introduction of disease germs. Carbon bisul- 

 phid is also used for this purpose, and it is exceedingly important to 

 know whether the fumigating process is likely to injure the vitality 

 of such seed. 



Seeds are protected from external injury by a skin or coat which 

 is thicker and more impermeable in some kinds than in others. 

 Further protection is afforded to some species by the fact that their 

 embryo or germ is surrounded by a firm mass of food material 

 composed of starch and various proteid or oily substances. Some- 

 times this material is deposited wholly in the thickened seed leaves 

 or cotyledons as in the case of the pea. On the other hand the 

 embryo or "chit" of corn, rye, wheat, barley and other grains lies 

 upon the surface just below the coat. Such seeds are more suscep- 

 tible to injury. Owing to these differences it is necessary to test the 

 effect of the carbon bisulphid upon each of the kinds which for any 

 reason require treatment. 



The length of time seeds must be treated with the fumes of car- 

 bon bisulphid depends not only upon the resistant power of the insect, 

 but also upon its method of attack. In the case of the pea weevil the 

 larva is embedded within the immature seed, becoming entirely sur- 

 rounded by the seed coat during its development, hence a treatment pro- 

 longed over twenty-four hours ma}^ be necessary to destroy the weevils. 



COMMERCIAL METHOD OF TREATING SEED WITH CARBON BISULPHID. 



Seedsmen treat peas and other "buggy" seeds on a large scale by 

 placing the bags containing the seeds in a fireproof, practically air- 

 tight building devoted to that purpose, setting shallow pans holding 

 carbon bisulphid in various parts of the room near the ceiling. After 

 being thus subjected to the fumes for about twenty-four, sometimes as 

 long as forty-eight hours, the room is opened and thoroughly aired. 



Some writers have advocated pouring the liquid through a pipe 

 inserted into the center of the bulk of seeds ; others suggest the use 

 of a ball of cotton, soaked with the chemical and plunged into the 

 middle of the pile of seeds. Both of these methods are open to 

 objection owing to the fact that the liquid comes in direct contact 

 with some of the seed which takes it up readily, rendering such seed 

 extremely liable to injury from the water which is left behind, if not 

 from a superabundance of the gas itself. Furthermore, carbon 

 bisulphid is a very heavy gas and the upper stratum of seeds treated 

 in either of these ways is likely to receive too little of the fumes to 

 destroy the insects. 



Our experiments were made with thirty-three different varieties of 

 grains and vegetables, five of cotton, two of peas, three of Indian 



