1917] 



DO UB T—ILL UMINA TING GA S 



217 



I 



peciosa. — With illuminat 



20,000 ppm caused 



some 



Populus deltoides.' 



000 ppm caused some leaf fall, and 



to fall; 8000 ppm caused epinasty. 

 With illuminating gas, 35,000, 2^.000 



other leaves died and fell off; 



ppm 



Ficus elastica. — With illuminating gas, 20,0c 

 older leaves to fall during treatment; 8000 ppm < 

 older leaves to fall about a week after treatment. 



Figs. 5, 6. — Fig. 5, Ricinus communis: plant at right, appearing normal, stood 



for 2 days in 50 ppm carbon monoxide; plant at left stood in 8 ppm ethyl 



for 2 



response 



note that direction of leaf blades is altered as well as that of petioles; fig. 6, Roots 

 (Pyrus communis at right; P. Mains at left): the 3-pronged root of pear has had 100 

 liters of illuminating gas forced into the soil during 40 days; notice swollen condition 

 of underground parts, also numerous "tubercles"; the root of apple received 160 



uminatin 



similar to that of pear. 



Croton tiglhim var. Sanders. 



ppm 



illuminating 

 leaves: 8000 



000 



000 ppm 



slight epinasty. 



Tulipa (several varieties). — With illuminating gas, ic 

 caused injury of the flower buds and the tips of the younger leaves 

 rolled up; 4000 ppm caused no visible injury. 



7 These were cuttings rooted in sand and grown in flower pots. 



