20 Lewis Knudson 



were selected. In work of this character it is essential to use onl}^ seed 

 of high germinating ability. The contaminations that occurred were due 

 largely to the introduction of dead seeds. 



RATE OF DIFFUSION OF CARBON DIOXIDE THROUGH COTTON PLUGS 



Molliard (1907) made some experiments to find out whether or not the 

 cotton plugs used in the culture tubes impeded the diffusion of carbon 

 dioxide into the plant chamber. He placed in the plant chamber small 

 open vessels containing barjiia water. He found that the cotton plugs 

 impeded the diffusion of carbon dioxide, since the barji;a water in the 

 plugged chambers absorbed only about one-fourth of the carbon dioxide 

 absorbed by the bar3i;a water in the open chambers. 



In an attempt to verify ]\Iolliard's results the writer placed wide- 

 mouthed bottles containing barj'ia water in the large cylinders, two of 

 which were open and two closed. No good results were obtained, since 

 the carbonate precipitate which formed at the surface interfered with the 

 absorption of the carbon dioxide. Consequently the baryta water was 

 replaced bj^ a solution of potassium hydroxide of a specific gra^dty of 1.27. 

 After a period of four days it was found that the potassium hydroxide in 

 the plugged cylinder had absorbed only one-third as much carbon dioxide 

 as that in the open cylinder. The cotton plugs, therefore, do impede the 

 diffusion of carbon dioxide, and consequently for all this work it was 

 essential to observe precaution in providing plugs of uniform compactness. 



IXFLUEXCE OF CEETAIX SUGAES OX GROWTH OF CORX (ZEA MAYS L.) 

 J. Laurent (1904), and Maze and Perrier f 1904), investigated the absorp- 

 tion of sugar by corn. Their results, while clearly establishing the utiliza- 

 tion of various sugars, do not give any idea of their respective assimila- 

 bility. Maze and Perrier state that saccharose is of more value than 

 glucose, but the e\ddence is not conclusive, since in the presence of glucose 

 abnormal plants developed in two cases and a normal plant in the third 

 case. In the dark the plants seemed to utilize saccharose, lactose, glycerin, 

 and starch in the order named. 



In the following experiments the influence of the hexoses glucose and 

 fructose, and the disaccharides saccharose and maltose, was noted. In 

 one experiment the plants were gro-^m in the laboratory, being maintained 

 in a dark chamber, while in the second the plants were grown in the green- 

 house. The assimilability of the sugar was judged by noting its influence 



