BY G. P. DARNELL-SMITH. 873 



dark brown liyphfe; on tlie sin-face, aerial liyplifp are sent up, 

 covering the wliole witli a light grev nivceliuni (Plate Ixxxiv., 

 fig.l). 



Upon agar impregnated with water-extract of orange-peel, an 

 intermediate type of growth was obtained (Plate Ixxxiv., fig. 2). 

 The fungus grew well but not luxuriantly, and there was little 

 production of aerial hyplije. 



In these cultures, pycnidial formation began after about seven 

 days, and ripe spores were obtained after thirteen days: but, in 

 the glucose-agar, where growth was luxuriant, spore-produotion 

 was much delayed. 



Production of Pycnidia and Spokes. 



When grown upon a medium that is thoroughly moist, the spores 

 that are formed in the pycnidia are expelled, and appear upon 

 the ostiole in a mass. This mass is whitish in colour, viscid and 

 semi-translucent. Usually it is globular, but it may take the 

 form of a truncated cone. When placed in water, the spores do 

 not readily separate from the mass, 'i'hese spore-masses may be 

 found in nature if the fruit is continually surrounded by a damp 

 atmosphere. Much more generally, however, the spores are 

 produced in pycnidia surrounded by a dry atmosphere. They 

 do not then emerge till a drop of moisture falls upon the pycni- 

 dium, whereupon tliey escape in a thin stream. Observed in a 

 hanging drop, they are seen to separate and spread themselves 

 at spaces almost equidistant from one another over the surface 

 of the drop, as if they were mutually repellant; and no two 

 spores are found to remain in juxtaposition. This separation is 

 probably brought about by surface-tension. Normally, the pyc- 

 nidia are produced upon the peel of oranges, and tlie ostioles 

 open at the surface. A .surface-view of a pycnidium, with an 

 ostiole in the centre, is shown in PI. Ixxxv., fig.3. 



If, however, affected oranges be kept under a bell-jar, and 

 remain free from attack by other fungi, they shrink somewhat, 

 and the peel becomes harder. The mycelium of the fungus 

 penetrates the whole of the pulp, which becomes black in colour, 

 and pycnidia are formed in abundance throughout the tissue. 



