616 



SCIENCE 



[N. S. Vol. XLII. No. 1087 



the entire volume of " egg sea-water." The 

 presence of eggs at the bottom of the bottle 

 makes impossible the thorough mixing which 

 should precede the taking of a sample. 



Sea-water which has stood over eggs in 

 shallow beakers exposed to the air always 

 gives much lower values for oxygen content 

 than ordinary sea-water at the same tempera- 

 ture. The difference is of the same order of 

 magnitude as the amount of oxygen used by the 

 eggs in an hour. But it is not due to oxygen 

 consumption, for the " egg sea-water " may be 

 siphoned off and allowed to remain several 

 hours in contact with air, so that equilibrium 

 is certainly established. The difference is of 

 course in part due to the iodine absorption of 

 " egg sea-water," but not wholly so. For if we 

 test a representative sample and obtain the 

 necessary correction for iodine absorption, a 

 difference still remains. If we assume that our 

 method is accurate, we are led to the conclu- 

 sion that the solubility of oxygen in sea-water 

 is lowered by some substance or substances 

 secreted by, or dissolved away from the eggs. 

 This is not at all unusual, if we remember that 

 Findlay and his collaborators have shown that 

 many colloidal substances exert a well-marked 

 influence on the solubility of gases.^ Granted 

 that our conclusion is correct, no method of 

 measuring oxidations that depends on a change 

 of oxygen tension (e. g., the Warburg-Siebeck 

 method^) is accurate. For any such method 

 assumes that the oxygen solubility of the sea- 

 water remains constant. 



Another method of making determinations 

 was devised in the summer of 1914. It was 

 found that the iodine-absorbing substances 

 normally given off by Arbacia eggs are col- 

 loidal. They do not diffuse through celloidin 

 or parchment membranes. In the measurement 

 of egg oxidations, therefore, the eggs may be 

 enclosed in celloidin tubes instead of being 

 allowed to lie free in the sea-water. Tubes of 

 about 10 c.c. capacity and of narrow bore fit 

 nicely into 300 c.c. bottles. At the conclusion 



^Jour. Chem. Soc. Trans., XCYII., 536, 1910; 

 CI., 1,459, 1912; CIIL, 636, 1913; CV., 291, 1914. 



« 0. Warburg, Zeit. f. physiol. Chemie, XCII., 

 231, 1914. 



of an experiment, the tube containing eggs is 

 taken out, the bottle is fiUed to the top with 

 sea-water of known oxygen content and is 

 tested for oxygen by the Winkler method. The 

 use of the celloidin tube has another advantage, 

 in that oxygen determinations may be made in 

 the same bottle in which the eggs were kept. 

 Thus, siphoning is unnecessary and there is no 

 error from this source. The tube method is, 

 however, open to the objection that in the case 

 of sea-urchin eggs at least, development can 

 not take place if the eggs are too closely packed. 

 Without modification it can therefore not be 

 used for the measurement of oxidations during 

 cleavage. 



Determinations have been made both by this 

 tube method and by adding corrections for 

 iodine absorption. The results gained so far 

 are not sufficiently accurate to warrant publi- 

 cation. They do show, however, that partial or 

 complete cytolysis produced by dilute sea-water 

 causes not an increase, but a decrease of 

 oxidations.^ 



L. V. Heilbrunn 



Woods Hole, Mass., 

 July 26, 1915 



A BACTERIAL DISEASE OF WESTERN WHEAT-GRASS. 



FIRST ACCOUNT OF THE OCCURRENCE OF A 



NEW TYPE OF BACTERIAL DISEASE 



Iisr AMERICA 



A VERY unusual type of bacterial disease has- 

 been found occurring on western wheat-grass, 

 Agropyron smithii Eydb., in the Salt Lake 

 VaUey, Utah, and has been given considerable 

 study by the writer during the current season. 

 Although affected plants are usually somewhat 

 dwarfed, the most striking characteristic of 

 the disease is the presence of enormous masses 

 of surface bacteria which form a lemon-yellow 

 ooze or slime. Sometimes this bacterial slime 

 appears in small droplets, but very often it is 

 spread over the surface of the upper portion 

 of the plant including the sheath, upper inter- 

 node and inflorescence. The glumes which are 

 badly attacked reveal bacterial layers of slime- 



' The tube method can not be used for completely 

 eytolyzed eggs, as the egg pigment wanders- 

 through the walls of the celloidin tubes. 



