November 25, 1921] 



SCIENCE. 



521 



both man and horses and common in France 

 and occasionally in America, is identically 

 the same species and should be called by the 

 name first used by Hektoen in this country. 



A butter having only a few yeasts and 

 molds, when other conditions are favorable 

 is a safer hazard for shipments and storage 

 is the claim of F. W. Bouska and J. C. Brown 

 of Chicago in their pajyer on " Yeasts and 

 oidia in pasteurized butter." Creameries 

 which have the best commercial reputation 

 for their butter also have the lowest yeast 

 and mold counts. These two men give 

 methods for sampling and counting butter 

 which they have recently devised. 



The late Dr. Edw. Birge presented his study 

 on the activities of certain bacteria in sewage. 

 He believed that some bacterial forms can be 

 found which will play an important role in 

 the treatment of sewage, and that the time 

 will come when septic tanks will be seeded as 

 alfalfa fields and cream vats are seeded now. 



A method for the detection of pasteurized 

 milks is described in detail by Dr. W. D. 

 Frost, of the University of Wisconsin. The 

 addition of a special dye stains the blood 

 cells, always present in pasteurized milks. In 

 raw milks the cells 'will not be stained. 



A strong plea for the thorough investiga- 

 tion of all waters whose potability is ques- 

 tioned, and for thoroughly trained investiga- 

 tors experienced in laboratory and field work, 

 is put forth by H. A. Whittaker, of the Uni- 

 versity of Minnesota, in a paper on the " In- 

 vestigation of drinking water supplies." 



A. L. Amott, a commercial milk expert in 

 Chicago, has given much time, energy and 

 thought to " The milk supply of Chicago," 

 and discusses the source of supply, amount, 

 production, transportation, city distribution, 

 prices, farmers' organizations, and milk in- 

 spection. He calls attention to the improve- 

 ment of the milk supply and the lowered 

 baby death rate in recent years in Chicago. 



B. W. Hammer, of the Iowa Agricultural 

 College, in a paper on " The bacteriology of 

 ice cream," summarizes the knowledge of 

 such points as number and kinds of bacteria, 

 sources of materials, effect on the bacteria 



during freezing, hardening and holding, sof- 

 tening and rehardening. He also treats of 

 the manufacture of ice cream with a low 

 bacterial count, and the relation of ice cream 

 to the public health, and bacterial standards. 



SPECIAL ARTICLES 



THE QUANTITATIVE BASIS OF THE POLAR 



CHARACTER OF REGENERATION 



IN BRYOPHYLLUM 



When the defoliated stem of a plant of 

 Bryophyllum calycinum is cut into as many 

 pieces as it possesses nodes, each piece will pro- 

 duce shoots from the two dormant buds of its 

 node and roots at its basal end. When a long 

 piece of stem possessing 6 or more nodes is cut 

 out from such a plant only the most apical 

 node will produce shoots from its two buds 

 while the other nodes will show no or only in- 

 considerable growth. The question is. Why do 

 all the nodes except the most apical fail to pro- 

 duce shoots when they are part of a long piece 

 of stem, while they would each produce shoots 

 when isolated? This is the problem of polarity 

 in regeneration in its simplest form. 



Earlier biologists, especially Sachs, have sug- 

 gested that this polarity is due to the fact that 

 the ascending sap carries the substances needed 

 for shoot regeneration and that if a piece of 

 stem is cut out from a plant the sap must col- 

 lect at the apex and thus give rise to the shoots 

 at the most apical node. This explanation is 

 only satisfactory if the assumption is added 

 that in the case of the stem of Bryophyllum 

 practically none of these substances reach the 

 dormant buds in the nodes below the most 

 apical one. The problem is how to furnish a 

 scientific proof for this suggestion. This can 

 be done by treating this problem from the view- 

 point of chemical mass action. 



The formation of new shoots in an isolated 

 node of a defoliated stem of Bryophyllum can 

 only be the result of synthetical processes the 

 velocity of which depends for a given tempera- 

 ture and degree of moisture upon the relative 

 mass of the material reaching the dormant buds 

 of the node in the unit of time. The material 

 required for growth will be taken from the sap 

 reaching the node. The disappearance of this 



