42 



CAUSE AND NATURH OF CROWN-GALL 



Iii looking over the slide it is observed that the nuclei are ab- 

 normally large in certain cells, most usually in cells more or 

 less adjacent to the meristem. Other nuclei appear as if caved 

 in on one side, the nuclear membrane being pressed into the 

 nuclear bod)''. A somewhat similar observation has been made 

 by Cavara," 7 who found that the mycelium of certain parasitic 

 fungi not only cause the nuclei of infested cells to enlarge and 

 assume various irregular forms before their final dissolution, 

 but that the effect was apparent on the nuclei of adjacent non- 

 infested cells as well. By a close inspection of these cells in a 

 freshly mounted specimen, the protoplasmic contents appears 

 vacuolar and frothy, or in some instances as a fine network of 

 granular strands (Fig. 19). 



Fig. 19. -Cells of the young gall in fresh unstained section viewed in water ; show- 

 ing the frothy, vacuolar protoplasm of the Plasmodium (Magnified same as scale; 

 scale = 10 u). 



It is imperative, if free-hand sections are studied in water, 

 that they be examined the first few moments after mounting, on 

 account of the effect of the water on the protoplasm. If exam- 

 ined in a y % per cent, solution of glucose, the sections may be 

 satisfactorily studied for some time. 



Under favorable conditions, if a fairly thick section of a young 

 gall be quickly prepared by cutting with a dry razor, placing 

 on a dry cover-glass, and immediately inverting over a moist 



37 Cavara, Dott. Fridiano. — Ipertrofie ed Anonialie Nucleari in seguito 

 a Parassitismo Vegetale. Revista di Patologia Vegetale, Vol. V, p. 238. 



