MISCELLANEOUS: TUMORS IN ABSENCE OP PARASITES 481 



Indies, and here the phenomenon is probably due to the alka- 

 line by-products of some undiscovered parasite. I also know 

 from my crown-gall inoculations that a true cambium devel- 

 oped in the bast of tobacco plants may give rise to tumor tissue 

 and to shoots ("Embryomas in Plants," 1. c.) and fromjhese 

 results it would seem as though wood and bast respectively must 

 be developed from cambium in a slightly alkaline medium andjn 



FIG. 360. Chestnut bark injection of 1914 by Caroline Rumbold showing 

 in cross-section islands of xylem in the phloem: (1) 1913 wood (free^from tyloses); 

 (2) 1914 wood (full of tyloses); (3) 1915 wood (free from tyloses); (4) cambium; 

 (5) phloem; (6) islands of wood in the phloem; (7) more phloem; (8) cork: 

 (9) injected (killed) area, 3-oo g-m. LioCOs being the substance used. Photo- 

 graphed by the writer from a section made and stained by Dr. Rumbold. 



a slightly acid medium and that to reverse the ordinary process 

 it is onl}>- necessary to change the reaction. If this should prove 

 true it would help perhaps to explain certain curious phenomena 

 of wood and bast distribution observed in the stems of lianas and 

 sometimes in other plants (See Jour. Agr. Res., Vol. VI, No. 

 4, Plates XX and XXI). By injecting a solution of sodium 

 bicarbonate into cabbage stems I obtained hard woody cylinders 



31 



