January 14, 1916] 



SCIENCE 



73 



SPECIAL ARTICLES 



PERIDERMIUM HARKNESSII AND CRONARTIUM 

 QUERCUUM 



Inoculations of Pinus radiata with secio- 

 spores of Peridermium harhnessii on Pinus 

 radiata made in the spring of 1913 resulted 

 in tj-pical galls during the same year. In the 

 spring of 1915 some of these galls bore secia of 

 Peridermium harhnessii. The check plants 

 remained sound. 



The myceliujn of Cronartium quercuum on 

 the evergreen Quercus agrifolia overwinters in 

 the old green leaves and in early spring pro- 

 duces sori of uredospores in a circle around 

 the old Cronartium spots; the uredinial sori 

 on the young leaves are the results of infection 

 from the sori on the old leaves. If Peri- 

 dermium harknessii connects with Cronartium 

 quercuum, we have here a case of facultative 

 heteroecism in both generations. 



E. P. Meinecke 



OFricE OP Investigations in 

 Forest Pathology, 

 Bureau of Plant Industry, 

 San Peancisco, Calif. 



a simple demonstration of the reduced 

 vapor pressure over a solution 



W AND S are two small glass crystallizing 

 dishes. W is half filled with water and S with 

 a strong solution of some salt. P is a piece of 



B 



W 



P 



plate glass and B is a bell jar. For equilibrium 

 the pressure of the vapor above S would have 

 to be less than that above W. Por this reason 

 the water gradually distills from W into S. 



This result is so obvious that the experiment 

 has no doubt been carried out before. How- 

 ever in a recent brief examination of the litera- 

 ture of the reduction of vapor pressure by 

 solution I have found no reference to it, al- 

 though Moser^ clearly indicates the possibility 

 of such an experiment. In his work he used 

 two U tubes, one for the water and one for the 

 solution. One end of each tube was closed, 

 and the open ends were joined — so that with a 

 connection to an air pump these open ends 

 formed a fork. Moser says: 



Das Lumen dieses Gabelrohrs ist eng, ein bis 

 ZTvei Millimeter, um eine Ueberdestilliren des 

 Dampfes vom Wasser zur Losung zu erschweren. 



In my experiment, which I carried out three 

 years ago, the dishes W and jS^ were about 5 

 cm. in diameter and jS contained a solution of 

 about 1 g. of sodium chloride to each 5 g. of 

 water. Vacuum wax was run around B where 

 it rested on P, but no attempt was made to 

 reduce the air pressure in B. The apparatus 

 stood in a room at ordinary laboratory tem- 

 perature from January 26 to March 21. At 

 first I set out to examine the rate at which 

 the liquid surfaces changed their levels, but 

 the sides of B were not smooth enough to 

 admit of making through them any readings 

 that were worth while. At the start the levels 

 were about the same, and after somewhat 

 less than two months the surface of the solu- 

 tion was 9.0 mm. higher than that of the water. 



Arthur Taber Jones 

 Smith College, 

 January 23, 1915 



THE AMERICAN MATHEMATICAL SO- 

 CIETY 



The twenty-second annual meeting of the society 

 was held at Columbia University on Monday and 

 Tuesday, December 27-28, 1915. Seventy-two mem- 

 bers attended the four sessions. President E. W. 

 Brown occupied the chair, being relieved by Profes- 

 sor Edward Kasner. The following new members 

 were elected: Professor W. E. Edington, University 

 of New Mexico ; Professor J. L. Gibson, University 

 of Utah; Dr. W. E. Milne, Bowdoin College; Pro- 

 fessor L. J. Eeed, University of Maine. Nine ap- 



1 Wied. An., 14, p. 73, 1881. 



