874 LIFE HISTORY OF PHOMA CITRICARPA, 



The hypliae even penetrate the outer coat of the testa of the 

 seed, and pycnidia are there produced (PL Ixxxv., fig. 4). A 

 somewhat similar phenomenon is observed when the fungus is 

 grown upon an orange rind-extract agar-slope in a test-tube. At 

 first, the mycelium grows near the surface, and pycnidia are 

 produced tliere; but, later, the hyph?e produce submerged pyc- 

 nidia, which may eject their spores as spore-masses into the 

 surrounding medium; in these cases, the ostiole appears to have 

 no particular orientation. 



It is noteworthy that oranges affected with Phoma citricarpa 

 and free from any other disease, if kept under a bell-jar, give off, 

 in the course of several days, very little moisture; but if they 

 are attacked by Penicillium italicum (to which attack they are 

 peculiarly liable in the presence of Phoma cit7'icarpa), a large 

 quantity of moisture condenses upon the surface of the bell-jar 

 in a few hours. 



Structurk of the Mycelium. 

 The mycelium exhibits much diversity. The extreme tips may 

 be pointed or round, the hyphse being thin, hyaline, and almost 

 devoid of septa. Further back, the liyphse become somewhat 

 suddenly thicker, the septa become more numerous, and the 

 colour is olive-green. In the older hyphse, the septa are very 

 numerous, the colour is dark greenish-brown, and the contents of 

 the cells granular; the cells may be oblong, or round, and often 

 carry numerous, short, round, protuberances (PI. Ixxxv , fig. 5; 

 PI. Ixxxvi., fig.6). 



Structure of the Spores. 

 Two kinds of spore are produced. Both kinds may be pro. 

 duced in a pycnidium or one kind only. They differ considerably 

 in size. The large spores are those described by McAlpine^ 

 whose measurements, in regard to the size of these spores and 

 the pycnidia, T can confirm. These spores are usually hyaline, 

 with granular contents; they have, however, frequently a greenish 

 hue. The cell-wall is very thin. They may have one or two 

 nuclei, generally there are two, and these are placed opposite to 

 one another adjacent to the cell-wall in the region midway 



