29 



that the lemon groves must be picked over several times during 

 the ripening season, the largest and most fully developed speci- 

 mens being taken off usually in August or September, according 

 as experience dictates. In handling these it is almost impossible 

 to keep them from being bruised or slightly scratched or even 

 pricked by thorns. Such abrasions in the epidermis, however 

 slight, are sufficient to permit the entrance of the fungus. 



THE COLOURTNG HOUSE. 



The colouring houses for the lemons are small structures, usually 

 about 12 feet wide by 14 feet long and 10 or 12 feet high. They 

 are double walled and built with a steel roof. The sun shining 

 on this roof causes the temperature of the building to rise. By 

 means of ventilation at the bottom and top the cool air is allowed 

 to enter at the floor and the hot air to pass out at the ridge of the 

 roof. By means of these ventilators the temperature is kept from 

 reaching too high a degree. At night the openings which permit 

 ths cold air to enter are closed, and if the outdoor temperature 

 happens to be quite cool the ventilators in the roof are also closed. 

 In this way the temperature of the colouring house causes a very 

 rapid ripening of the lemons, the fruit turning yellow in a few 

 days. The evaporation from the lemons causes the air to become 

 humid, creating a most admirable condition for germinating any 

 Colletotrichitm spores that may be adhering to the fruit. Spores 

 that happen to be near an abrased place in the epidermis of the 

 lemon will find an entrance and produce the disease in the fruit. 

 The drying of the fruit which occurs at the latter end of the colour- 

 ing period causes the affected portions to become depressed brown 

 areas when the disease has progressed sufficiently. 



When the lemons have been permitted to mature rather fully 

 the process in the drying house is of short duration. No matter 

 how short it is, however, it is always sufficiently long to permit 

 fungus infection. When the period between infection and removal 

 of the fruit from the colouring house is of short duration, the spots 

 have not had time to collapse and become brown, making it im- 

 possible to detect the disease when the fruit is being graded and 

 put into crates ; consequently a considerable percentage of lemons 

 infected with Colletotrichmn is packed and shipped to the markets 

 and the diseased spots develop in transit. 



Experiments with infected lemons show that the fungus continues 

 to develop, even if they are placed in the dry atmosphere of a 

 living room, and that a spot is produced. These spots when ex- 

 amined under a microscope showed no fungus spores, and only a 

 few mycelia were found in the tissues of the lemon rind adjoining 

 the blackened area. On lemons under normal conditions, such as 

 those in a crate on the way to market or in a storeroom, these spots 

 develop very rapidly. Freight cars or the holds of vessels usually 

 superheated, bringing the temperature up to that needed for the 

 most rapid development of the fungus. Crates of lemons that 

 were started out from the packing house during August, 1 902, 



