CROWNGALL STUDIES SHOWING CHANGES IN PLANT 

 STRUCTURES DUE TO A CHANGED STIMULUS 



[PRELIMINARY PAPER] 



By Erwin F. Smith, 



Pathologist in Charge, Laboratory of Plant Pathology, 



Bureau of Plant Industry 



Some recent experiments with crowngall have led to a number of 

 discoveries which may be summarized as follows : 



First, as everyone knows, the tendency of cambium is not simply to go 

 on indefinitely producing more cambium but to elaborate out of its 

 embryonic elements formed structures, tracheids, wood vessels, wood 

 fibers, ray cells, sieve tubes, etc., all having a definite arrangement and 

 a well-defined polarity, but when internodal stem cambium is inoculated 

 with the crowngall organism (Bacterium iumejaciens) the ordinary physio- 

 logical tendencies are upset, as already shown in 1911 and 191 2,* and 

 several very interesting new phenomena make their appearance: (i) The 

 elements of the formed or mature tissues are produced in less numbers 

 than ordinarily, and these elements have lost the whole or a considerable 

 part of their polarity, so that the most bizarre complexes of twisted and 

 distorted tissues arise; (2) the parenchymatous elements are greatly 

 increased in number and reduced in size, since under the bacterial stimu- 

 lus many of the cambium cells appear to have lost all power to produce 

 mature tissues and at the same time have acquired a new growth impetus, 

 a tendency to an uncontrolled, pathologically embryonic, cell multipli- 

 cation, the result of which is a tumor of indefinite extension — the ordinary 

 naked crowngall, containing the distorted formed elements above referred 

 to and in addition exhibiting a marked hyperplasia of the parenchyma; 

 (3) correlative with these changes, over which the plant has no control, 

 is a tendency to open wounds and to early decay and also to the formation 

 of daughter tumors. 



Second, when, by means of very shallow needle pricks, similar inocu- 

 lations are made into the internodal cortex of young stems (the so-called 

 fundamental tissue, which is still in a growing condition) a similar cell 

 proliferation occurs, the elements of which are very small in comparison 

 with those from which they have developed, because under the changed 

 stimulus they are kept embryonic and are compelled to divide soon after 

 previous divisions, so that they can never reach maturity either in size 



1 Smith, Erwin F., Brown, Nellie A., and Townsend.C.O. Crown-gallof plants: its cause and remedy. 

 U. S. Dept. Agr. Bur. Plant Indus. Bui. 213, 215 p., 36 pi. 1911. 



Smith, Erwin F., Brown, Nellie A., and McCulloch, Lucia. The structure and development of crown- 

 gall: a plant cancer. U. S. Dept. Agr. Bur. Plant Indus. Bui. 255, 60 p., 109 pi. 1912. 



Journal of Agricultural Research, Vol. VI, No. 4 



Dept. of Agriculture, Washington, D. C. Apr. 24, 1916 



ds G — 77 



(179) 



