212 BOTANICAL GAZETTE [march 



by nematodes. 



Results of treatments 



In the following records, plants are arranged in the order of 

 their sensitivity to gas. All amounts of gas indicated are in parts 

 per million of air (ppm) . 



Lathyrus odoratus. — With iooo, ioo, 75, and 50 ppm illuminating 

 gas, the leaves turned yellow and died. Ethylene 8 ppm caused 

 the leaflets to fall off; 5 ppm caused the leaves to become yellow 

 and die; 2 ppm caused death of the older leaves; and 0.1 ppm 

 still caused noticeable injury, although less than in the other cases. 



Salvia splendens. — With 25,000 ppm illuminating gas, the older 

 leaves fell off, while the younger ones showed epinasty; 9000 and 

 8000 ppm caused epinastic response of the petioles; 1 1000 ppm 



1 In all cases of epinasty the leaves drooped, but the blades and petioles remained 

 rigid. In some cases the halves of the blades folded together somewhat (fig. 4)- 





3. Epinasty of petioles. — Suitable concentrations of illuminating 

 gas and of ethylene produced epinasty in petioles or flower stalks. 

 In Lycopersicum and Salvia this response is often so marked as to 

 produce complete spiral coils. The petioles of Ricinus, Datura, 

 Coleus, and Hibiscus, and the flower stalk of calla lily also showed 

 epinasty in traces of these gases. The bending may be near the 

 blade or the bud, as in calla lily leaf and flower; all along the petiole, 

 as in most younger leaves; or very near the stem, as in most older 

 petioles (figs. 1-5). 



4. Proliferation tissue in lenticels, leaf scars, etc. — In the pres- 

 ence of traces of illuminating gas or of ethylene, soft spongy tissue 

 developed in the lenticels (Hibiscus and Sambucus), at leaf scars 

 (Lycopersicum) , or at more or less extensive regions along the stems. 

 In the roots of the apple and pear the abnormal tissue developed 

 just outside the vascular cylinder, but it is not determined whether 

 it was produced by the cortex or the pericycle. Deep longi- 

 tudinal cracks developed in the bark of the stem. These appeared 

 on the apple, pear, ash, and Hibiscus, and to a less degree in Sam- 

 bucus, Grevillea, and cottonwood. 



5. Root tubercles. — Traces of these gases produced tubercle- 

 like growths on the roots of Grevillea, Sambucus, Populus, apple, 

 pear, and Hibiscus. In the tomato similar tubercles are produced 









