424 



SCIENCE. 



[N. S. Vol. XXIII. No. 585. 



tions on this subject. He has fed plants 

 with cane sugar, potassium, calcium and 

 magnesium salts, and reports that he has 

 obtained positive results. He, however, 

 adds that other factors must be taken into 

 consideration, as the presence of oxygen, ex- 

 posure to light and the maintenance of a 

 certain temperature. 



Certain more or less fanciful notions have 

 heretofore prevailed with regard to the in- 

 fluence of chemicals on the color of flowers. 

 The blue-flowered form of Viola lutea has 

 been supposed to owe its color to the pres- 

 ence of zinc in the soil. The blue color in 

 flowers of hydrangea has been attributed to 

 the presence of an excess of iron or alum in 

 the soil, and it is a common practise among 

 rose growers to treat the soil with a solution 

 of ferrous sulphate for intensifying the 

 color of red roses. 



About November 1, 1904, through the 

 courtesy of Dr. George T. Moore, the au- 

 thor began a series of experiments in the 

 greenhouses of the U. S. Department of 

 Agriculture at Washington, for the purpose 

 of determining the effects of certain chem- 

 icals on the color principles of plants. The 

 plants selected for study were carnations, 

 roses and pansies. The following chemicals 

 were used: Aluminum and potassium sul- 

 phate, aluminum phosphate, aluminum 

 sulphate, aluminum and ammonium sul- 

 phate, iron and ammonium sulphate, iron 

 citrate, iron salicylate, iron malate, iron 

 succinate, ferrous sulphate, potassium 

 cyanide, potassium hydrate, potassium ni- 

 trate, potassium iodide, water of ammonia, 

 ammonium nitrate, acetic acid, citric acid, 

 formic acid, malic acid, salicylic acid, phos- 

 phoric acid, sulphuric acid and iodine. 



The work thus far must be regarded as 

 more or less preliminary, as the experiments 

 showed that it is necessary to establish 

 control conditions in order to determine 

 the effects of the chemicals supplied, apart 



from other factors. Some effects have al- 

 ready been noted, but these could perhaps 

 be ascribed to other factors than the chem- 

 icals used. For instance, in the case of La 

 Prance roses the petals became of a uni- 

 form pink color when the plants were sup- 

 plied with iron citrate and citric acid. 

 Maroon roses became dark red when the 

 plants were supplied with phosphoric acid, 

 iron and ammonium sulphate or sulphuric 

 acid. In fact, the color of the maroon roses 

 approached that of the crimson roses when 

 treated with sulphuric acid, and they also 

 tended to singleness. 



Channels of Entrance and Types of Move- 

 ment in Bacterial Diseases of Plants: 

 Dr. EEvyiN F. Smith, United States De- 

 partment of Agriculture. 

 Using the blackboard for purposes of 

 illustration, the speaker discussed the 

 various ways in which bacteria enter the 

 living plant, viz., through wounds and 

 through natural openings. The question 

 whether there is ever any entrance of the 

 bacteria except through tissues injured by 

 other causes was also discussed. It is still, 

 perhaps, a matter of doubt whether in case 

 of certain stomatal infections which take 

 place when drops of water stand on the 

 plant for a long time, there may not be 

 suffocation of a few cells in the substomatie 

 chamber prior to the multiplication of the 

 bacteria. Such, however, does not appear 

 to be the case, and certainly in water-pores, 

 where the tissues are accustomed to be 

 bathed in excess of water an infection con- 

 ditioned exclusively on preliminary suffo- 

 cation would seem to be improbable. The 

 writer obtained rather promptly, viz., 

 within a few days, numerous small, round, 

 dead spots on cotton leaves sprayed under 

 tents with water and then with pure cul- 

 tures of Bacterium malvacearum. But 

 these spots, which he regards as genuine 



