CAUSE AND NATURE OF CROWN-GALL 



yv*v 



THE FRUCTIFICATION. 



Under favorable conditions the plasmodium collects in vari- 

 ous surface regions of the gall. At this time not only the 

 cells, but occasionally the intercellular spaces as well, are filled 

 with a complex network of protoplasmic strands (Fig. 27.) 

 The portions of the gall from which the plasmodium has with- 

 drawn show the cells entirely 

 empty, and even in unstained 

 sections are in marked contrast 

 to the infested areas. 



If a gall be carefully exam- 

 ined at this time or a little 

 later, minute globules (one to 

 three in cases observed) may 

 be seen in the process of form- 

 ing on the surface above one 

 or more of the regions noted. 

 These are developing sporan- 

 gia and resemble minute glob- 

 ules of exuded gum. At first 

 they are a clear, transparent 

 amber, but twelve to twenty 

 hours after their appearance 

 they become clouded from the 

 development of the contained 

 spores. Four to eight hours 

 later they are ruptured by the 

 bursting of the peridium. 



During the fall of 1S99 I had 

 the opportunity to examine a 

 number of galls from the Glendale orchard and others from 

 Tucson at the time the plasmodia came to the surface and 

 developed fruit. In not a single case was I able to find the 

 fructification on galls immediately after cutting them from the 

 trees. The galls upon which the parasite fruited were cut 

 from the trees in November, at which time they were of large 

 size, but had not as yet begun to become discolored. The speci- 



<JV> 



w w 



Fig. 27.— Section through the surface 

 tissue of the gall, showing the Plasmo- 

 dium migrating to the surface prior to 

 fructification. (Magnified same as scale ; 

 divisions of scale = 10 n ) 



