216 BOTANICAL GAZETTE [march 



Hibiscus rosa-sinensis. — With illuminating gas, 9000, 8000, and 

 4000 ppm caused all leaves to fall; new leaves developed in 2-3 

 weeks after removal from the case; the lenticels on the stem were 

 filled with spongy white tissue; with 1000 ppm the older leaves 

 fell, and the younger leaves showed epinasty; with 100 ppm only 

 slight epinasty was evident. With ethylene, 8 ppm caused dis- 

 tinct epinasty; 2 ppm caused slight epinasty, but this is near 

 the limit for response. With carbon monoxide, 12.5 ppm caused 

 no response. 



alypha tricolor. — With illuminating gas, 25,000 ppm 



some 

 ppm 



8000 and 1000 



Acacia horrida. — With illuminating gas, 8000 ppm caused fall 

 of many leaves; 1000 ppm caused fall of some leaves several days 

 after treatment. 



Euonymus japonicus. — With illuminating gas, 20,000 ppm 

 caused most of the leaves to fall; 8000 ppm caused the older 

 leaves to fall; 1000 ppm caused a few of the older leaves to fall. 



Citrus decumana. — With illuminating gas, 20,000 and 8000 ppm 

 caused most of the leaves to fall after removal from the case; 

 1000 ppm caused the older leaves to fall. 



Zantedeschia ethiopica. — With illuminating gas, 40,000 ppm 

 caused the flower spathe to become somewhat discolored, but the 

 plant seemed uninjured; 10,000 ppm caused epinasty in the young 

 leaves, the petioles being arched next to the blade; 9000, 8000, and 

 1000 ppm caused the youngest leaf and the peduncle to show 

 epinasty as above. With ethylene, 5 ppm caused slight epinasty 

 of the youngest leaf; 2 ppm caused no response. 



Pelargonium zonule. — With illuminating gas, 25,000 and 4,000 

 ppm caused no visible response during 4 days of treatment, but all 

 leaves fell in 3-6 days after treatment had stopped; 6 100 ppm 

 caused no response. With ethylene, 8 and 2 ppm caused no 

 response. With carbon monoxide, 12.5 ppm caused no response. 



Begonia luminosa. — With ethylene, 8 ppm caused some epinasty 

 at the base of the leaf blade. With carbon monoxide, 50 ppm 

 caused no response. 



6 When new leaves developed, they were without the variegated zone. 







