Carbon Dioxide in Maturation, etc., of Seeds. 421 



This retardation or inhibition produced by C0 2 was shown to be unaccom- 

 panied by injury. The seeds used in these experiments fall into two classes. 

 In the first class the seeds germinated at once after removal from the 

 inhibitory C0 2 pressures (beans, cabbage, barley, peas, onions). In the second 

 class the inhibition continued indefinitely after the removal of the inhibitory 

 C0 2 pressures, and was terminated only by complete drying and re-wetting, 

 or by the removal of the testa. In this class a lowering of the degree of 

 permeability of the testa to gases by the action of CO2 is indicated, a change 

 which would have two results : (1) a reduction in the amount of oxygen 

 reaching the embryo, and (2) a relative rise in the actual CO2 pressure in the 

 embryo tissues. The condition of prolonged inhibition after removal to air 

 produced in Brassica alba is strikingly suggestive of the condition of seeds 

 often met with in nature, the germination of which is delayed in spite of 

 suitable conditions of temperature and water. The results obtained in the 

 laboratory with Brassica alba seeds were reproduced in the soil in natural 

 conditions by CO2 arising from decaying vegetable matter. The high C0 2 

 content of the soil air in these experiments was found to continue for a 

 considerable period. Attention was called to the importance of these facts in 

 agriculture. 



LITERATURE CITED. 



1. Loeb, 'The Mechanistic Conception of Life,' 1912. 



2. Starling and Lane-Claypon, "An Experimental Enquiry into the Factors which 



determine the Growth and Activity of the Mammary Glands," ' Roy. Soc. Proc.,' 

 B, vol. 77, pp. 505-522 (1906). 



3. Czapek, "The Anti-ferment Reaction in Tropistic Movements of Plants," 'Annals of 



Botany, 3 vol. 19, pp. 75-98 (1905). 



4. Shull, " Oxygen Minimum and Germination of Xanthium Seeds," ' Bot. Gaz.,' vol. 52, 



pp. 455-477 (1911). 



5. Crocker, "Bole of Seed Coats in Delayed Germination," 'Bot. Gaz.,' vol. 42, 



pp. 265-291 (1906). 



6. Nobbe and Hanlein, " Ueber Resistenz von Samen gegen die ausseren Factoren der 



Keiniung," ' Landw. Versuchs-Stat.,' vol. 20, pp. 63-96 (1877). 



