Pomona College Journal of Economic Botany 



33 



stops at a fork in the branch. The lemon trees, showing the effects of 

 the disease most, are those which have the greatest number of fallen leaves 

 and bare twigs. 



On the. Fruit. (Fig. 17) : The fruit-spot, commonly called lemon spot, 

 orange-spot, and pomelo-spot or anthracnose is the most easily recognized. 

 On the lemon it usually develops in the packing house and is first simply a dull 

 green blotch, remaining so after the lemon has turned yellow in curing. Later 

 the center of the spot, which may enlarge, becomes from a sickly-yellow to a 

 brown color and is softer than the margins, which have retained the same 

 firmness as the rest of the lemon. This stage develops the black or dark- 

 brown acervuli, which appear in the center of the spot, giving it a dark color. 

 The tissues begin to sink, forming a depression in the center of the spot. 

 The fruit may keep in good condition when thus infected for a long time 

 without any apparent progress in the work of the fungus and again it 

 may decay very rapidly. The green spot may not develop to form the fruiting 

 stage until after the lemons have been placed upon the market, so may 

 admit of the marketing of the fruit, but it places it in the lowest grade. 



It will be interesting to note that many have considered this spot a 

 result of sweating and not a fungus at all, but it is the wither-tip brought out, 

 perhaps, in greater abundance, by sweating, than under normal conditions, 

 which has given rise to this belief. 



The so-called "red-spot" (See Fig. 18) on the lemon has never been de- 

 scribed outside of California. However, it has received considerable atten- 

 tion from Dr. Woods and Prof. Rolfs — men who are the best authorities 

 known on wither-tip. These men have all pronounced it as a result of this 

 fungus. 



The infection takes place at any point on the rind in the form of minute 

 dark brown or cinnamon red spots. At first these may be so small that they 

 cannot be detected without the aid of a hand lens and may be very scarce. 

 The spots grow in size and increase in number until the whole rind is 

 speckled. Later they become confluent and spread over the entire surface 

 giving the fruit a dark-brown or even black appearance. The disease does 

 not seem to affect the pulp of the fruit at all, but simply disfigures the rind so 

 as to make it unfit for market. Each red spot, in the earlier stages, pro- 

 duces a sunken area which is very characteristic of this stage. 



The attack is more often on the fruit known as "tree-ripes" — fruit that 

 has ripened on the tree — but it is not an uncommon thing to find it also 

 abundant upon the green fruit. It was first noticed on the trees' affected 

 with "Gummosis," and it has not infrequently been attributed to that as a 

 cause. It may be that it was most abundant here because of the weakened 

 condition of the tree, brought about by the gumming, which enabled the 

 fungus to find the most favorable conditions for growth. 



Of the spot Dr. Woods writes: "Before leaving California I arranged with 

 Mr. Powell to have a lot of the lemons and grapefruits showing the tear- 

 stain and browning and other effects of the wither-tip fungus forwarded to 



