352 DISEASES OF CROP-PLANTS 



be of advantage to cut off an inch of the stalk when the fruit 

 is brought in from the field and then sear the freshly cut end or 

 dip it in melted adhesive wax. The fruit should be laid out 

 for twenty-four hours to cool and dry before packing. It is 

 obvious that the method of packing should be such as to prevent 

 contact between, or movement of, the fruit, while permitting free 

 circulation of air, and that storage and stowage should be in 

 well-ventilated places. 



J. E. Higgins, in Hawaii, and Vera H. Charles, in Washington, 

 have experimented with the use of formaldehyde gas for fumiga- 

 ting pineapples previous to storage, the object being to kill the 

 spores adhering to the outside of the fruit. Both report very 

 considerable improvement in the keeping qualities of fruit so 

 treated. 



Papaw. 



The papaw is generally distributed and common throughout 

 the islands, grown usually in a scattered way as a fruit tree. In 

 Montserrat a peasant industry exists in the collection of coagu- 

 lated milk from the unripe fruits of plants which occur in con- 

 siderable numbers on uncultivated land. Attempts which have' 

 been seen to establish papaws in field cultivation suggest that 

 insect and fungus troubles would become severe under these 

 conditions, and plots of superior imported varieties have in 

 several cases failed owing to their greater susceptibility to 

 disease. Only casual attention has as yet been given to the 

 affections which occur. 



Black Leaf-Spot. 



The leaves of the papaw are liable to heavy infestation with 

 the fungus named below, which produces thickly sown and 

 conspicuous spots, rounded except where they impinge on a 

 vein, ranging in size from mere specks to about 3 mm. diameter ; 

 on the upper surface they are dark brown, with a whitish centre 

 in the larger examples, below they are a uniform velvety 

 black. 



The fungus as usually met with is confined to a conidial form, 

 Asperisporium Caricce (Speg.) Maub., the uncertain taxonomic 

 position of which is shown by the variety of genera (Cercospora, 

 Fusicladium, Scolecothricum, Epiclinium, Pucciniopsis) in which 

 it has been placed. 



The short vertical cylindrical-clavate conidiophores are 

 crowded side by side in a dense and even layer on the under 

 surface of the spot. Each has several minute papillae on its 

 rounded summit, and bears single terminal conidia in succession. 

 The conidia are thick-walled, rough, irregular in outUne, often 

 more or less pear-shaped, and i, 2 or occasionally 3-celled. A. 



