REACTION OF THE PLANT. 



93 



an enlargement of the nucleus, often to double the normal size, and often a change of shape 

 to spindle form. In such tissues the nuclei stand out very prominently in the small cells, 

 being the most conspicuous objects in the section. This size, however, may be a character- 

 istic of extreme youth rather than of disease, since the writer has also seen large nuclei in 

 the tissues of the growing point of healthy daisy-plants. The disorganization of the nucleus 

 in root-nodules of Leguminosae seems to be 

 preceded by some enlargement. The subject 

 requires further study. 



CHANGES IN THE CHROMOSOMES. 



Following Farmer's statements and similar 

 statements by other English students of malig- 

 nant animal tumors, the writer has been very 

 much interested to see whether the chromosomes 

 undergo any change in number or location in 

 the rapidly dividing cells of crown-galls and 

 similar plant tumors. The first studies were 

 made on peach tissues but here the nuclei are 

 so small that the determination of the normal 

 number of chromosomes proved difficult. At- 

 tempts to get tumors on onion, the normal 

 cytology of which is well known, also failed. 

 The Paris daisy was finally selected. This has 

 large nuclei and the normal number of chro- 

 mosomes appears to be 1 6. A study of slides 

 prepared from very young stages of tumors 

 taken from this plant has thus far shown noth- 

 ing definite except that at least a part of the 

 divisions are mitotic. 



The most interesting thing made out in 

 connection with the cell morphology is that 

 first pointed out by Tourney for the almond 

 gall, viz., the occurrence of more than one nucleus 

 in a cell without any evidence of the beginnings 

 of a cell-wall between them. Tourney figures 

 2, 3, and 4 nuclei in a cell. The writer has seen 

 two well-developed ones in cells of the rose gall. 



ANTIBODIES. 



Fig. 29.* 



This is almost a wholly unworked field. 

 The writer has seen nothing corresponding 



to the self-limited infectious diseases of animals, or which indicates that plants can be 

 preserved by vaccines. The subject is of extreme interest theoretically. Practically it is 

 of less importance, owing to the great number of plants which would have to be inoculated 

 and their slight value individually in comparison either with the labor involved or with 

 the individual value of the higher animals. One attack does not confer immunity on any 

 plant so far as known to the writer. But in this connection it should be understood that 

 we know as yet very little of all that is to be known about this group of plant diseases, and 



*FiG. 29. Tumor on sugar-beet produced by a Schizomycete plated from crown-gall of peach. Inoculated Mar. 

 ii, 1908. Photographed May 4, 1908. Nearly natural size. Five plants were inoculated and all contracted the 

 disease. Previously the organism had been passed by the writer twice through peach-trees with production of galls. 



