536 



SCIENCE 



[N. S. Vol. XXXII. No. 825 



an overbalanced supply of nitrogen plus 

 moisture, they readily destroy such straw 

 and the grain is proportionally shrivelled. 

 They penetrate such straws rapidly and 

 reach the seed at blossoming time and it is 

 cut off from the mother plant and can not 

 mature, even though in the straw there is 

 left much unorganized plant food. Just 

 in proportion as the fungi are capable of 

 penetrating the straw the seed is deterio- 

 rated. Straws will crinkle and fall down 

 when attacked by these diseases in a man- 

 ner very characteristic of crops on over- 

 fertile or over-worked soils, even though 

 there is a deficiency of moisture and of 

 soil fertility, while the same pedigree of 

 seed will stand strong and sturdy upon 

 soil of much richer character with refer- 

 ence to nitrogen and still produce plump 

 seed in the absence of the fungi. These 

 fungi are so common and persistent in 

 their nature in the soils of the northwest 

 ■that if any one of you will go out into the 

 stubble of an ordinary field where the 

 wheat grains were evenly distributed in 

 the drill row and of proper thickness of 

 planting, and if you find that a part of the 

 plants stool well and a large percentage 

 of them produce only single straws of more 

 or less weakness and smaUness of diameter, 

 I can assure you that you will find the 

 roots of those unstooled plants in a diseased 

 condition, whether you pull them before 

 heading or after the grain is cut (usually 

 -black-footed, creosote colored or gray to 

 mouldy). Exceptions are so few as to 

 prove the rule. These diseases are of such 

 nature as to largely account for the off 

 grades in grain, for I have found in wheat 

 plants which are sufficiently affected for 

 the' parasites to reach the seed that the 

 grain will be off color, and will be graded 

 .by the elevator men as bleached and blis- 

 tered, ' ' black-pointed, " " white-bellied, ' ' 

 etc., even though ciired under canvas and 



having suffered from no moisture effects 

 whatever, either before or immediately fol- 

 lowing harvest. 



One, and perhaps two, of the most de- 

 structive of these parasites produce the ef- 

 fects known as black point in durum 

 wheat, a disease which is very promi- 

 nent and becoming much more common of 

 late years than when the grain was first 

 imported into this country. Durum 

 wheats, because of their peculiarity of 

 straw, are able to produce plump wheat 

 and yet carry diseases inside to such extent 

 that 15 to 25 per cent, of properly har- 

 vested and cured wheat will not germi- 

 nate. These diseases, especially the Fusa- 

 rium type, largely account for the low 

 germination of durum wheats. This I 

 have proven both by culture work and by 

 infection. The Fusarium diseases and 

 possibly alternarial diseases largely ac- 

 count for the so-called "piebald" wheat 

 or "white-bellied" wheat. I have previ- 

 ously claimed that moisture after the for- 

 mation or maturity of the berry was the 

 chief cause of this trouble. Others, notably 

 Professor Shutt, of Ontario, claim that 

 the loss of humus and nitrogen, causing a 

 fall in the proteid content of the berry, is 

 the cause, but I find that with the presence 

 of certain fungi and a certain amount of 

 moisture the result is almost certain, while 

 in the absence of the fungi and moisture 

 there is no piebald wheat, regardless of the 

 nitrogen content of the soil. 



All of these types of diseased grain 

 breed true, that is, a diseased grain will 

 carry the diseases to the soil, and if the 

 seed can germinate and the young wheat 

 plant can survive to the extent of produc- 

 ing seed, and the weather conditions are 

 just right for the growth of wheat, the dis- 

 ease will be manifested in the seed of the 

 progeny, and will persist in the soil so as 

 to attack the following crop of wheat. 



