552 Emerson: Macrophoma and Diplodia 



ning. In spite of such good growth pycnidia develop slowly and 

 sparingly on potato but very freely on cocoanut pith. It was not 

 possible to obtain young healthy cocoanut plants which could be 

 inoculated with pure Macrophoma in order to prove whether it 

 was parasitic or simply saprophytic. When fresh leaves from a 

 greenhouse were used for inoculation, moulds and other fungi 

 which were already established quite prevented the Macrophoma 

 from growing at all. 



In the development of the fungus, first a white film of my- 

 celium spreads quickly over most of the medium ; in about a 

 week parts become dark green and gradually black, and in ten 

 days to two weeks from the sowing the pycnidia are formed. 

 On cocoanut pith, bread or potato cultures these were often 

 quite above the substratum, even as early as eight or nine days 

 from the sowing, when they looked like tiny green bubbles cov- 

 ered with hyphae. Even in this immature condition the Macro- 

 phoma spores were abundant ; being pale green, granular and 

 often containing what appeared to be oil-drops, and seeming to 

 have more abundant contents than those from maturer pycnidia. 

 In a damp atmosphere the Macrophoma spores are apt to come 

 out of the mouth of the pycnidia and form a white mass. No 

 spores which resembled conidiospores were noticed, but there were 

 several other forms which seemed to be sclerotial or resting in 

 their function. Soon after the green color came in a culture, on 

 examining the mycelium it would be seen that a few cells or as 

 many as eight in a hypha had become round or oblong, thick- 

 walled, brown, sometimes quite rough, 25— 29/i x 8—1 8 /^. They 

 germinate very readily, putting out several tubes from one spore 

 (figure 4). Sometimes two of these will cling together and the 

 two might easily be mistaken for a Diplodia spore. Around the 

 outside of the pycnidium there is apt to be a mass of empty two- 

 celled bodies, one cell being slightly smaller than the other, as in 

 a Puccinia teleutospore. Possibly they are merely short, swollen 

 hyphae similar to the cells which make the outside wall of the 

 pycnidium. 



From the time the cultures were first obtained pure it was evi- 

 dent that the growths of MacropJioma and Diplodia were very much 

 alike, as had been suspected from their close association and the 



