BOTANICAL GAZETTE 



[JULY 



In stems this proliferation of cells became first evidentatthelenticels 

 by their increase in size and the protruding of white tissue, as shown 

 in the lower portion of the stem in fig. 7. Richter (12) has noted 

 a similar proliferation of tissue at the lenticels of Vicia villosa under 

 the influence of tobacco smoke. Stone's similar results have 

 been cited. In the roots this tissue was abundantly developed 

 in some cases, particularly in Hibiscus, which is shown in fig. 7, 

 where B and C are plants which were subjected to a slow stream 

 of illuminating gas for a period of 30 days. Fig. 8 shows detailed 

 structure of these proliferations in the roots of Hibiscus. The cork 



Fig. 7.— Hibiscus: A, control; B, C, treated with illuminating gas 



layer of the abnormal root has been sloughed off. Practically the 

 same morphological situation appears in this case as in Ailanl/ius 

 previously figured. 



A similar response by lilac is shown by drawings of fig. o. These 

 abnormalities were recorded for Hibiscus, lilac, Croton, Dicrvilhi, 

 Ricinus, Ulnius, and pear. 



An experiment similar to the foregoing was carried out with an 

 Ailanthus growing on the campus near the Hull Botanical Labora- 

 tory. The tree had a diameter of about 8 cm. and a height of 3 . 5 m. 

 At a short distance were other trees of the same species which served 

 as controls. Illuminating gas was admitted to the roots of the 



