i9i 7l DOUBT— ILLUMINATING-GAS 22$ 



lentum, Salvia splendens, Mimosa pudica, Ricinus communis, 

 Datura Stramonium, and Dianthus Caryophyllus. The response 

 of each is definite, striking, and not easily mistaken. 



2. Traces of gas (50 ppm of air) cause the epinastic growth of 

 the petioles of all these plants, with the exception of the last. The 

 flower buds of the carnations are blighted by these amounts. One 

 part of illuminating gas per 1000 of air causes leaf fall in the follow- 

 ing plants: Lycopersicum esculentum, Salvia splendens, Mimosa 

 pudica, Datura Stramonium , Ricinus communis, Coleus sp., and 

 Hibiscus rosa-sinensis. Both the amounts (50 ppm of air and 

 1 part per 1000 of air) are far below the limit of odor. Repeated 

 trials showed that it was impossible to detect less than 0.25 per 

 cent of illuminating gas (1 part to 400 of air) by the sense of smell. 



3. Amounts of ethylene corresponding to the gas mixture gave 

 similar responses; 2 ppm of air caused epinastic grow r th of the 

 petioles of Lycopersicum esculentum, Salvia splendens, Mimosa 

 pudica, Ricinus communis, and Datura Stramonium; 8 ppm of 

 air (equivalent to 200 parts of illuminating gas) caused some leaf 

 fall in the 5 plants named. 



4. Poa pratensis and Acer Negundo are very resistant to gas, 

 having shown no response to concentrations injurious to all other 

 forms tested. 



m 



there is enough present to be detected by odor: Caladium escu- 

 lentum, Lupinus perennis, Eriobotrya japonica, Phoenix canariensis, 

 Conocephalus sp., Canna, Achyranthes lindini, Alternanthera sp., 



6. The following 

 the soil: Pvrus Mains 



Polypodi 



Ulmus 



Populus deltoides, and 

 Catalpa, and Sambucus 

 of the stems below th 



Grevillea robusta, Catalpa speciosa, 

 ericana. Apple, pear, ash, elm, 



Elm, ash, and 

 iust above the 



surface of the ground. 



7. The following bedding plants are injured by gas escaping 

 into the soil: Lycopersicum esculentum, Salvia splendens,* Ricinus 

 communis, and Chrysanthemum hortorum. Chrysanthemum i- 



