Carbon Dioxide in Maturation, etc., of Seeds. 617 



of the maturing seed, while still upon the parent plant, may be due directly 

 to C0 2 inhibition or narcosis. In order to obtain evidence here an endeavour 

 was made to ascertain the actual CO2 content of ripening seeds. The method 

 adopted was suggested by Dr. F. F. Blackman, for whose advice and direction 

 during these researches I am deeply indebted. The technique of tbis method 

 for determining the amount of CO2 present in the tissues of seeds was as 

 follows : — 



Two lots of material of equal weight were taken in each experiment. 

 One lot was crushed to thin paste in a mortar and left exposed to the air for 

 40 to 80 minutes. It seemed from experiments that this time was sufficient 

 to allow the escape of the CO2 present in the tissue mash. A known 

 quantity of baryta was then added and a titration made with HC1. The 

 second parallel lot was crushed immediately under an equal quantity of 

 baryta and a similar titration made. 



The difference between these two readings invariably showed that more 

 baryta had been neutralised where the tissues had been crushed immediately 

 in contact with it than where the tissue was first exposed for some time to 

 air after crushing to a mash. These differences were taken as roughly 

 expressing the relative CO2 contents of the tissues used in these experi- 

 ments. 



The results obtained in a series of experiments made by this method to 

 ascertain the COo content of maturing peas and beans from fresh green pods 

 and of the same seed during its drying in laboratory air, are given in the 

 following table : — 



Table VIII. — The CO2 Content of Maturing Peas (Pisum sativum) and Beans 

 ( Vicia faba) when removed fresh from the Green Pod and during the 

 first few days of drying. 



Description of seed. 



Grammes of 

 H : per 

 100 grm. 

 of seed. 



Cubic centi- 

 metres of 

 CO., per 

 100 grm. of 

 seed. 



Eatio C0 2 H = in 

 tissues of seed. 



Peas fresh from the pod 



Peas after 4 davs in laboratory air 



Beans fresh from pod 



Beans alter 1 day's drying in laboratory air 

 Beans after 4 days' drying in laboratory air 



50 

 22 

 60 

 56 

 51 



54 

 145 

 51 

 46 

 41 



108/100 

 660,100 

 85/100 

 82/100 

 80/100 



In comparison with the above results the following Table gives those 

 obtained in a second series of experiments made to determine the CO2 



