THE CROWN GALL: TYPE 419 



the tumor is centrally located and then the plant may be killed 

 outright, but this is much less frequently the case than with 

 animals attacked by cancers, the anatomy and physiology of the 

 plant being specially unlike that of animals in that there is no 

 central digestive, nervous, or circulatory system subject to 

 attack, with a disastrous reaction upon the whole organism. 

 The nearest analogy to this is the growing point of centrally 

 growing soft plants like young sugar-beets. If the needle is set 

 in so that this is interfered with, as the big tumor develops, death 

 occurs within a few weeks. See Jour. Cancer Research, Vol. I, 

 No. 2, PL Vila All of the inoculated plants there shown died a 

 few weeks later. I have obtained the same results on tobacco. 



The organism causing this tumor occurs only inside of cer- 

 tain of the proliferating cells. When the cell divides, the or- 

 ganism is carried over into the daughter cells, in at least a part 

 of which it multiplies. It occurs in the cell in comparatively 

 small numbers and, owing to the granular nature of the proto- 

 plasm cannot be made out satisfactorily even with high powers 

 of the microscope. By means of gold chlorid impregnation 

 followed by formic acid we obtained a deep blue-black stain 

 in certain rod-shaped bodies in the tumor cells (Figs. 331, 332) 

 and for a time these were interpreted as the intra-cellular bac- 

 teria, but I now regard them as mitochondria. 



In 1916 the writer discovered crown galls bearing leafy shoots 

 and subsequently produced many by needle-puncture inocula- 



(2) On Paris daisy. 1911. Time, 73 days. Primary tumor at .Y on stem, 

 secondary tumors in 3 leaves. These were connected with the stem-tumor by 

 tumor -strands lying deep in the wood. % nat. size. (3) On Paris daisy. The 

 original tumors (X, X) have decayed and a new tumor has grown out below. 

 Stem dead. Time, 10 months, nearly. % nat. size. (4) Sunflower. Inoculated 

 in the disk when young (August 14, 1915) with isolation from the hop (4-day 

 agar-streak). A tumor -strand passed through the pith rupturing to the surface 

 below in two places that shown and as a small tumor in axil of Y. % nat. size. 

 (5) On Paris daisy. Cross-section of stem showing a primary tumor below and 

 a large green tumor-strand with thickening of wood on that side. The strand 

 was under strong pressure and protruded when the stem was cut. X 2. (6) 

 On Paris daisy. Inoculation made on stem below cut here shown. Observe 

 one-sided thickening of wood, and three tumor-strands which passed to as many 

 leaves, two fusing. The leaves, which bore secondary tumors, were cut away 

 some weeks earlier and from the stubs new tumors have grown out. Time, March, 

 1911. 



