34 Pomona College Journal of Economic Botany 



me. I had these carefully examined and found the fungus, Colletotrichum 

 glocosporioid.es, present in practically all cases." 



Concerning the same point, Mr. M. B. Waite, Pathologist in Charge of 

 the Bureau of Plant Industry, Washington, D. C, writes: "In the first 

 place there is no question about its (the disease on lemon twigs and 

 fruit sent to Mr. Waite for determination) being affected with the wither- 

 tip fungus, Colletotrichum. Spots were found with a little of the fungus 

 on microscopic examination, and upon culture tests the material was 

 found to contain considerable of the fungus. Ripe spores were found on old, 

 dry twigs, while the leaves and the fruit developed spores after being steril- 

 ized and covered with a dry bell jar." 



Figure 18. An orange branch killed by the wither-tip, some of the dead leaves still 

 hanging; a lemon showing red-spot caused by wither-tip. 



"I think the red spider is responsible for the spread of the fungus to a 

 considerable extent on the lemons this season, the slight injury produced by 

 the spider making an opening for the fungus to get into the skin of the 

 fruit." — P. H. Rolfs. 



On the orange the first symptoms appear as greenish or brownish irregular 

 blotches, resembling greatly those described on the lemon. These spots 

 grow rapidly while the fruit is still on the tree and may assume nearly half the 

 size of the fruit. (This being due to the fact that many spots become con- 

 fluent thus forming a single large diseased area. The average size, however, 

 is about that of a 25c-piece.) With age the center of the diseased area may 

 become lighter before turning a dark brown or black with the appearing of the 

 dark fruiting bodies. The area may be raised above the remaining surface 

 of the orange or it may sink to form a depression as is shown in the photo 

 (Fig. 17). 



