July 20, 1917] 



SCIENCE 



53 



panies the first few years of cropping upon new 

 land areas. 



All these statements have to do with the 

 fact that wheat in particular and most 

 cereal grains are attacked by certain para- 

 sitic fungi which have been usually consid- 

 ered saprophytes or semi-parasites. They 

 attack in such manner as to invade all parts 

 of the plant body, break down the tissues, 

 clog up the ducts, and rot off the roots, and 

 they are particularly destructive as the 

 seedling and stooling stages, and finally 

 cause blighting and shrivelling of seed. • 

 We have developed a particularly interest- 

 ing method of attempting to purify such 

 internally infected wheat grains and other 

 cereals by special methods of heavy seed 

 disinfection, aiming at seed-coat disinfec- 

 tion. The seedlings are then grown upon 

 agar just as one grows a pure culture of a 

 fungus or a bacterium. This allows proper 

 study of the root characters and other con- 

 ditions as affected by the organisms, and 

 makes it possible to separate uninfected 

 seedlings to be grown on purified soil. This 

 work has been associated with special stud- 

 ies upon soil and seedling purification in 

 many ways. The results of tests extending 

 over a number of years show that continu- 

 ous cropping to wheat and flax brings 

 about a continuous cumulative infection of 

 soil and seed. In flax the wilt fungus, 

 Fusarium lini, remains indefinitely in fer- 

 tile soil and makes it essentially sterile for 

 that crop. So, also, certain fungi of wheat 

 eat away at the roots and attack seedling 

 plants from the stubble or seed and through 

 accumulation in the seed carry always an 

 accumulating infection to new or cleaned 

 lands, undoing the proper effects of tillage 

 and crop rotation. 



A few of the genera particularly con- 

 cerned in the destructive work upon wheats 

 are Alternaria, Colletotrichum, Helmintho- 

 sporium and Fusarium. Each of these is 

 peculiarly destructive in its own way, and 



in certain years one or other may excel in 

 the destruction of the crop. 



To these attacks the wheat plant reacts 

 as best it can by the growing and sending 

 down of new roots, adventitious or brace 

 roots, as fast as the old ones die. Its fibrous 

 rooting capacity stands it well in hand, 

 with the result that, unlike flax, it usually 

 holds on to the ground and does not give an 

 absolute failure, though a very irregular 

 crop is characteristic. The disease gener- 

 ally known as scab falls under the group 

 known as Fusarial infections. These no 

 doubt spread from head to head to a cer- 

 tain extent, but by far the largest amount 

 of damage is done by direct attack upon 

 the roots- just as in flax-wilt and other 

 Fusarial wilts. I need not go further into 

 this phase of the subject. 



If the diagnosis is correct, we shall never 

 get the full benefits from the campaign for 

 a better agriculture until steps are taken to 

 rather suddenly and generally bring about 

 an actual compliance in better sanitary 

 methods of harvesting the crop and hand- 

 ling the soil and seed. 



Mr. Rockwell Sayre, of Chicago, has not 

 been wholly vsrrong in his campaign for 

 compulsory crop rotation laws. Our peo- 

 ple do not like to be compelled to do any- 

 thing. Perhaps the better method is to edu- 

 cate, but general education comes too 

 slowly to be effective in any sanitary meas- 

 ure. On small areas such as are occupied 

 in potato cropping and in intensive farm- 

 ing propositions the educational process 

 can be brought about and rather effectively 

 carried into operation, but with the great 

 cereal crops where practically three fifths 

 or more of the entire area of a state is put 

 under wheat and allied cereal culture, these 

 diseases, under present methods, run riot. 



Wliat to do : It is with a good deal of 

 temerit}^ that I offer the following sugges- 

 tions. I recommend through this congress 



