Influence of Carbon Dioxide in Maturation, etc., of Seeds. 609 



DESCRIPTION OF PLATE. 



Fig. 1. — Microphotograph of Cortex of Dog's Kidney at Rest, x 500. 

 Fig. 2. — Microphotograph of Cortex of Opposite Kidney after Activity, x 500. 

 Fig. 3. — Cat's Kidney. Drawing of glomerulus and tubules after activity, showing 

 dilatation of neck of tubule, x 500. 



The Controlling Influence of Carbon Dioxide in the Maturation, 

 Dormancy and Germination of Seeds. — Part II. 

 By Franklin Kidd, B.A., Fellow of St. John's College, Cambridge. 



(Communicated by Dr. F. F. Blackman, F.B.S. Received March 25, — 

 Read May 14, 1914.) 



CONTENTS. 



PAGE 



Introduction 609 



Section I. — Relation to Temperature of the Inhibitory Effect of Carbon Dioxide 



on Germination 610 



,, II. — Relation to Oxygen Pressure of the Inhibitory Effect of Carbon 



Dioxide on Germination 612 



„ III. — Carbon Dioxide as a Factor in the Dormancy of the Maturing Seed 



on the Plant 614 



(a) Arrested Development of Maturing Seeds not due to Lack 



of Moisture. Retarding Influence of the Testa 614 



(6) Direct Estimations of Carbon Dioxide Content of Maturing 



and Germinating Seeds 616 



„ IV. — Contrast of Depressant Action of High Partial Pressures of Carbon 

 Dioxide with Stimulating Effect of Low Partial Pressures. 



Carbon Dioxide considered as a Narcotic Agent 618 



„ V. — Influence of Carbon Dioxide in enforcing Dormancy in certain 

 Seeds which do not naturally have a long Dormant Phase. Seeds 



of Hevea Brasiliensis 620 



„ VI. — Biological Importance of Dormancy in Moist Seeds 622 



„ VII.— Summary and Conclusions 623 



Introduction. 



In the first part of this paper the influence of carbon dioxide in 

 inhibiting the germination of moist seeds was described. The results 

 obtained are summarised on pp. 623-625 of this paper. 



In the present paper the relation of this inhibitory effect of carbon 

 dioxide to temperature and oxygen supply is first to be examined, and 

 then will be studied further narcotic or inhibitory effects of CO2 as 



