Vol. XIII. No. 312. 



THE AGRICULTURAL NEWS. 



127 



merely to retard the growth of the plant, but when the 

 terminal bud is lost the plants are permanently deformed 

 and usually produce a much smaller and later crop than 

 normal individuals in the same field. 



In the most severe form of the disorder the young 

 seedlings lose the buds in the axils of the cotyledons as well 

 as the terminal bud. Such plants are unable to form 

 any true leaves, but the cotyledons increase in size and 

 the hypocotyl becomes much thickened. In some cases the 

 root begins to form a subterranean shoot, like those that 

 develop vegetative buds when plants have been killed to the 

 ground in the winter. When abortion of the bud takes 

 place higher up, so that the plants have one or two true 

 leaves, the blades grow much larger than usual and the 

 petioles become greatly elongated. If thinning be deferred 

 until the normal plants are 10 inches or a foot high it is 

 easy to distinguish and remove the deformed individuals and 

 leave only the healthy and vigorous ones. Under the usual 

 plan of thinning the cotton early it is much more difficult to 

 recognize and remove the injured plants. 



Susceptibility to leaf cut is usually limited to the 

 seedling and young plants less than 10 inches high. Some- 

 times the change from susceptibility to immunity is very 

 abrupt. Plants that have had every leaf injured up to the 

 sixth or eighth may then begin to put out entirely uninjured 

 leaves. These abrupt changes may affect whole rows or 

 fields of cotton, as if the later uninjured vegetation had 

 grown out after a hailstorm. Whether the plants become 

 immune to leaf cut simply because larger stature carries 

 the new growth farther away from the overheated soil, 

 or because a deeper root system affords a more regular 

 supply of moisture, or because the weather conditions 

 become more uniform as the season advances has not been 

 determined. All these factors may co-operate, or there may 

 be others as yet unsuspected. 



A few cases of abnormal individuals have been observed 

 where injuries very similar to leaf cut continued during the 

 whole life of the plant. Some of these plants were hybrids 

 and others were mutations, but all of them were abnormal 

 in other ways, as well as in the irregular texture of the 

 foliage. It seems not unreasonable to suppose that abnormal 

 plants should remain more susceptible to any external cond- 

 itions that have adverse effects upon the activities of the cells. 



Though all the different types and varieties of cotton 

 seem to be susceptible to leaf-cut injuries, certain differences 

 have been noticed. The leaves of the Durango cotton and 

 other Upland varieties are often injured much more seriously 

 than those of Egyptian cotton in adjacent rows, but at the 

 same time the Egyptian cotton may show a larger percentage 

 of abortion of terminal and axillary buds. The immunity 

 may lie in the improvement of conditions rather than in 

 an increased resistance on the pan of the plant. With the 

 plant lice injuries there is a gradual reduction of the amount 

 of distortion that the insects are able to produce, which may 

 indicate the development of a different kind of immunity in 

 this disorder. It is true that the plant lice usually disappear 

 as the season advances, but even when the insects remain 

 abundant the distortion becomes less as the plants grow 

 larger. conclusion.s. 



Leaf cut is a disorder of cotton seedlings characterized 

 by mutilation of the leaves and abortion of the terminal 

 buds. Leaf-cut has been confused with the distortion of the 

 leaves by plant lice, but the two malformations are readily 

 distinguished. 



Leaf-cut is in the nature of an environmental injury, 

 not due to parasitic organisms or to constitutional weakness, 

 but apparently connected with expo.sure to heat and dryness. 



All varieties of cotton are susceptible during the early 

 stages of growth. 



Though leaf cut is not fatal, it is responsible for much 

 damage by retarding the growth of the young plants. The 

 loss of the terminal buds interferes with normal habits of 

 branching, and the plants are permanently deformed. 

 Damage from leaf-cut can be avoided or reduced by 

 improved cultural methods, and the deformed plants can 

 be removed by later thinning. 



LIVE STOCK NOTES. 



BOVINE TUBERCULOSIS INVESTIGA- 

 TIONS. 



In the Report of the College of Agriculture and 

 th? Agricultural E.xperiment .Station of the University 

 of California (1912-13), the following summary is 

 published, describing the results of an investigation to 

 test the value of 'Bovovaccine' in immunizing cattle 

 to tuberculosis: — 



Bischoff and (Jompany, American agents for the 

 products of the Marburg Institute, Germany, have been 

 active in selling von Behring's bovovaccine to dairymen in 

 this State. In 1907 it seemed desirable to undertake some 

 experiments to determine its efficiency under California 

 conditions. 



Forty-five calves were secured for the purpose of this 

 experiment, measures being taken to obtain animals free 

 from tuberculous infection. Twenty-two of the calves were 

 treated with bivovsccine after the manner of von Behring 

 and twenty three were kept as controls. For a year the 

 calves were reared with precautions against tuberculous 

 infection. At the end of eight months all of the calves were 

 te.sted with tuberculin and none reacted. Even in the bovo- 

 vaccinated calves the hyper sensitiveness which usually exists 

 for a time in such animals had disappeared. 



After having satisfied ourselves that the herd was free 

 from tuberculosis, the forty-five animals were subjected to 

 infection by placing in their pasture cattle having open 

 tuberculosis. These were associated with the calves in a 

 20 acre pasture and in corrals where they came to be fed. 

 The first lot of tuberculous cows brought into contact with 

 the calves were five in number. Within six months these 

 cows had all died of tuberculosis. 



The following spring, ten more reacting cows, having 

 evidence of open tuberculosis, were introduced and the 

 infection experiment carried through until the young vaccin- 

 ated cattle and the controls were between two and a half 

 and three years old. Details of the tests need not be given 

 other than to summarize the final results. They were all 

 autopsied, most of them were killed for beef at about three 

 years of age, under federal inspection. 



Of the twenty-two vaccinated cattle, ten were tuberculous. 

 Of the twenty-three non vaccinated cattle, fourteen were 

 tuberculous. Bischoff and Company wrote us that if another 

 vaccination had been made when the animals were about a 

 year old, their immunity would doubtless have been increased 

 sufficiently to protect them from infection. And there is 

 reason to believe that this might have been the case. 

 However, even if frequent injection of bovovaccine would keep 

 cows immune, it would be impracticable to vaccinate mature 

 dairy cows with virulent human tubercle bacilli. Our 

 conclusions are that some immunity was produced by the use 

 of bovovaccine, but that this immunity did not remain to 

 any appreciable extent after the third year. We cannot 

 recommend the use of bovovaccine to stock owners. 



