628 EXPERIMENT STATION RECORD. [Vol. 38 



be the best for that plant were subjected to several gases and to air by 

 different methods. 



The cultures supplied with oxygen, nitrogen, and air showed no departure 

 from open controls or cultures sealed in accordance with the method employed 

 by Briggs and Shantz (E. S. R., 25, p. 214), growth rate and dry matter 

 production being essentially the same and practically all the plants setting 

 seed. The degi'ee of aeration of buckwheat appears to be of little influence 

 under such conditions. This point, it is thought, may be of value in general 

 water culture practice. The plants continuously treated with carbon dioxid 

 wilted in a few hours and died in a few days. A test with the admission of 

 air after the first day resulted in a partial recovery, although the plants 

 remained permanently smaller than the controls. 



The effect of deficient soil oxygen on the roots of higher plants, B. E. 

 Livingston and E. E. Fkee (Johns HopJcins Univ. Circ, n. ser., No. 3 (1911), 

 pp. 182-185). — During the last three years, experiments have been in progress 

 regarding the oxygen requirement of the isolated and controlled root systems 

 of higher plants, the aerial portions being exposed to the atmosphere. 



The response of the root systems apparently differs greatly with the species. 

 The first noticeable effect of oxygen deprivation is an interference with water 

 absorption by the roots, complete cessation occurring in 24 lioure in case of 

 Coleus hlumei and Heliotropium peruviannm. Examination of the root sys- 

 tems of injured plants showed them to be dead and in some portions disinte- 

 grated. Coleus may be revived and may form a new system of roots, which 

 always starts from the base of the stem. The earliest symptoms of injury 

 appear on plants having the largest root systems. Apparently the crucial con- 

 dition is limitation of the oxygen supply per unit of root surface or volume. 



The evidence suggests that the cause of injury by oxygen exclusion is an 

 interference with the respiration of the protoplasm of the root cells. The suc- 

 cess of Salix under deprivation of oxygen raises the question whether the 

 respiration of its roots may not be anaerobic. 



The effects of certain mineral poisons on young wheat plants in three-salt 

 nutrient solutions, E. E. Frke and S. F. Teelease (Johns Hopkins Univ. Circ, 

 n. ser., No. S (1917), pp. 199-201). — The authors, having experimented with 

 wheat plantlets in the nutrient solution found by Shive (E. S. R., 34, p. 333) 

 to be the best for the production of dry weight of tops in case of wheat, give 

 the results in tabular form, with discussion. 



Most of the elements employed failed to show any stimulating effects. It is 

 suggested that the solution employed is itself slightly toxic because of its 

 high magnesium content. It produces plants showing modifications character- 

 istic of magnesium poisoning, but gives the best yield of dry weight. This, 

 ■with other observations, suggests that the best production of dry matter by a 

 plant occurs as a result of slight poisoning. Work on the Canada field pea is 

 said to have confirmed this suggestion in some degree. Apparently either 

 magnesium or boron will serve, and it is suggested that other poisons may 

 prove to be as efficacious in this respect. 



Symptoms of poisoning by certain elements in Pelargonium and other 

 plants, E. E. Free (Johns Hopkins Univ. Circ, n. ser.. No. 3 (1911), pp. 195- 

 198). — In tests made by the author regarding symptoms of poisoning shown by 

 P. zonule and other plants under the action of poisonous elements in different 

 concentrations, it was found that arsenic, barium, bromin, cobalt, copper, lead, 

 manganese, nickel, silver, uranium, vanadium, and zinc showed no determinable 

 poisonous effect for any concentration with any plant employed. INIanganese 

 and zinc slightly improved both color and condition in Pelargonium. Arsenic 



