Pomona College Journal of Economic Botany 



75 



show them to be filled with a clear gum-like substance. The pockets resemble 

 water blisters and are more or less oblong in shape and vary from one-quarter 

 to one-half an inch in length. 



Multiple Buds— (Fig. 29 C). Is the name used by Mr. Floyd for the abnormal 

 number of buds which arise from a single axil. There may be from two to four thus 

 formed, where in a normal case only one bud would be found. These buds are 

 sometimes accompanied by an exudation of gum which may in time completely 

 cover them with a reddish-brown stain. 



Figure 29. Die-back on Orange: A, showing gum pockets; B, cross-section of a 

 Valencia, showing gum at core; C, twig showing multiple buds and dead tips. 



Bark Eruptions — In more advanced stages the gum pockets erupt and allow the 

 gum to flow out in numerous places over the stems. Eruptions also occur from the 

 leaves, showing that the gum does not always come from well defined gum pockets. 

 The gum that oozes out forms small patches, regular or irregular, of resin-like 

 substance, which becomes reddish-brown and which is so characteristic of this dis- 

 ease. This gum soon hardens and presents its natural appearance for a long time. 

 Excellent dry specimens of this stage may be preserved in the laboratory indefi- 

 nitely. 



Die-Back — (Fig. 29 C). The young twigs die back in a very marked manner 

 as described above, and as is well shown in the accompanying illustrations. The 

 dead portion may remain light in color, but is more often covered with a black 

 saprophytic fungus growth. The length of the dead portion varies with the size 

 of the limb, but usually continues from the tip back to the first well defined branch. 



