28 



Lewis Knudson 



to plants grown in the light. In the following experiment a series of 

 various concentrations of lactose were tested, with results as shown in 

 table 6. A large number of seeds were sown in each culture tube, and 

 in no case was there increased growth. Lactose is therefore not assimi- 

 lated by timothy when the plant is grown in the light. 



INFLUENCE OF A MIXTURE OF LACTOSE AND SACCHAROSE 



In the preceding experiment it was noted that lactose exercises no 

 beneficial effect on timothy. In the following experiment a mixture 

 of lactose and saccharose was employed. With 0.4 per cent of saccharose 

 added to 2 per cent of lactose there is a marked increase in growth, and 

 still greater growth results when 0.8 per cent of saccharose is added to 

 2 per cent of lactose. It appears, therefore, that there is an election 

 of saccharose by timothy, and that this sugar is directly assimilated 

 by the plant. The results are given in table 7: 



TABLE 7. Influence of a Mixture of Lactose and Saccharose on Growth of 



Timothy 



(Duration, thirty days) 



Culture solution 





Total 



Number 



dry 



of 



weight 



plants 



(milU- 





grams) 



60 



79 



69 



63 



64 



84 



52 



66 



68 



76 



60 



85 



68 



124 



Average 



dry 

 weight 



per plant 

 (milli- 

 grams) 



1 



Check (no sugar) \ 2 



3 



Lactose, 2 per cent < i 



Lactose, 2 per cent, -\- saccharose, 0.4 per cent 



Lactose, 2 per cent, -f- saccharose, 0.8 per cent 



.32 

 .07 

 .31 



.27 

 .12 

 .42 

 .82 



CONCLUSION 



The results here reported, and the general results of three other exten- 

 sive experiments with timothy not here reported, demonstrate that the 

 sugars glucose, maltose, and saccharose are absorbed and assimilated by 

 timothy. Lactose is apparently not utilized at all. 



