SOME MORPHOLOGICAL RESPONSES OF THE HOST 
TISSUE TO THE CROWNGALL ORGANISM 1 
By A. J. Riker 2 
Instructor in Plant Pathology, University of Wisconsin 
INTRODUCTION 
In a previous paper (r ) 3 the writer has described inoculation studies 
of crowngall on tomato stems in which it was observed that needle 
punctures immediately released liquid which flooded the neighboring 
intercellular spaces and formed water-soaked areas in the surrounding 
tissue. Liquid which was expressed from a tomato stem was found to 
exert a positively chemotactic influence upon the crowngall organism, 
Bacterium tumefaciens Smith and Town. When applied to the surface 
of the puncture, they entered and distributed themselves through the 
water-soaked area. The galls which developed in the mature tissue 
were found to coincide closely in outline with these water-soaked regions., 
When the water-soaked regions were extended by bruising, the bacteria 
migrated to the limit of the continuous channel of liquid, which was as 
far as eight centimeters in some cases. The bacteria were observed 
consistently in situ in an intercellular position, both in free-hand and 
in paraffin sections from five series of inoculations which were examined 
at two-day intervals from the time of inoculation until distinct hyper¬ 
plasia, hypertrophy, and vascular elements developed. 
The earlier paper made no attempt to describe the abnormal host tissue. 
Herewith is given a report, previously briefly noted (2, j), of the studies 
made upon the responses of the host tissue to the bacteria, including a 
description of such phenomena as “secondary tumors” and “tumor 
strands.” 
HISTOLOGICAL STUDIES OF CROWNGALL ON TOMATO 
At the time when observations were made on the location of the 
bacteria, an opportunity was provided for studying the course of develop¬ 
ment of the gall. This was done in the following manner. In a pre¬ 
liminary series, five inoculations were made on each stem of two dozen 
tomato plants. A different plant was examined every day and notes 
were taken relative to changes that occurred during the formation of 
the galls. In three subsequent series the examination was made only 
every other day because the changes were too slow to show any marked 
difference in twenty-four hours. These four series varied somewhat in 
the speed with which certain developments appeared, but the order 
was practically the same. For the most part, examinations were made 
on free-hand sections mounted in lacto-phenol (equal parts of phenol, 
1 Received for publication April 16, 1923. 
* The writer takes pleasure in expressing his indebtedness to Dr. L. R. Jones and Dr. G. W. Keitt, Ox 
the University of Wisconsin, and also to other members of the faculty, especially to Dr. E. J. Kraus, for many 
valuable suggestions in the prosecution of these studies. 
* Reference is made by number (italic) to “ Literature cited,” p. 435. 
( 425 ) 
Journal of Agricultural Research, 
Washington, D. C. 
ahr 
Vol. XXVI, No. 9 
Dec. 1, 1923 
Key No. Wis.-»s 
