12 



SCIENCE 



[N. S. Vol. LIII. No. 1358 



imder different climatic conditions, or the 

 breeding of varieties of cereals resistant to 

 diseases? We might well consider the stu- 

 pendous losses from parasitic fungi of cereals. 

 There never was a time when research on 

 cereals and other agricultural crops was as 

 important as it is to-day. We have, on a 

 large scale, undertaken the removal of the 

 barberry in the wheat-growing section of the 

 country, because the plant pathologists are 

 convinced that the common barberry is an im- 

 portant factor in rust production. And yet, 

 I was confronted with the frequent statement 

 by practical men in western Minnesota that 

 there is no barberry in this particular section. 

 I certainly saw none in the immediate area 

 to speak of, although there was some bar- 

 berry thirty miles to the south. I could 

 not make the questioner see the importance 

 of the barberry in connection with grain 

 rust. Some seasons no doubt there are 

 actually viable uredo spores on grasses. 

 The point, I think, we should determine 

 to convince the wheat grower on is this: 

 are the uredo spores viable in weedy grasses, 

 and how far can the uredo spores be 

 carried? The farmer who loses $3,000 on a 

 quarter section of land in a single year of 

 wheat-growing wants some solution of the 

 problem. It is the duty of the government 

 and the botanist to solve the problem for the 

 country. Unless this is done by extermina- 

 ting the barberry, the breeding of resistant 

 varieties and the elimination of weedy grasses, 

 the growing of spring hard wheats will be a 

 thing of the past, and the farmer will be 

 forced to turn his attention to the growing of 

 other cereals, not subject to rust. The gov- 

 ernment and the states directly interested, can 

 well afford to spend a half million dollars an- 

 nually until the problem is solved. 



WEEDS 



The subject of weeds is related to that of 

 plant disease. It greatly interests the farmer 

 and gardener. The farmers of the United 

 States, at least in some sections, have en- 

 deavored to remove by legislation some of the 

 injurious weeds, expecting, of course, that the 



law would be obeyed and the weeds would soon 

 be eliminated, but instead they are constantly 

 increasing. As illustrations of weed legisla- 

 tion I need only remind you that some twenty- 

 five years ago nearly all the northwestern 

 states made it illegal to permit Russian thistle 

 to grow. During these twenty-five years it 

 has spread from the Atlantic to the Pacific. 

 In Washington and Colorado where the condi- 

 tions are suitable it covers the ground on 

 little travelled roads and on the plains. In 

 Iowa we made an effort by legislation to re- 

 duce the infested areas of quack grass, but 

 it has so increased that the farm values in 

 some cases are reduced because of its presence. 

 During the past two seasons I have received 

 a large niunber of specimens of knapweed 

 (Oentaurea solstitialis) from many points in 

 Iowa and northern Missouri, distributed 

 largely through alfalfa seed. Buckhom (Plan- 

 tago lanceolata) is rapidly interfering with 

 clover culture in Iowa. 



We have described weeds and how to 

 eradicate them, because this is the kind of in- 

 formation the farmer wants, but we have not 

 solved a single one of the important problems 

 in connection with weeds. Weeds have an im- 

 portant bearing on the crops produced. The 

 small ragweed no doubt reduces the efficiency 

 of the Iowa pasture during the autumn 

 months fully one half, the weeds of corn fields 

 frequently cut the yield one third. How these 

 yields are reduced has not been determined. 

 How much do we know about the mechanical 

 interference of weed roots and the agricul- 

 tural crop? So far as I know, there is ab- 

 solutely no data on the subject. Water is 

 an important factor in crop production ; there- 

 fore, a study of transpiration is of importance 

 in connection with a study of weeds. It has 

 been pointed out by Livingston that trans- 

 piration is practically a simple fimction of 

 the leaf surface and that the total transpira- 

 tion is a measure of the growth of a plant, 

 whether it is one growing in a waste place or 

 of economic importance. 



Kesselback makes it clear that weeds such as 

 sunflower use more than three times as much 

 water per plant as corn, while water used per 



