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J. J. TAUBENHAUS 
lot. Lot I was used as a check. Lot II was inoculated with a pure 
culture of Lasiodiplodia tubericola E. & E. The method of the inocula- 
tions here recorded was to insert bits of mycelium of pure culture 
into slits in the epidermis and cambium made with a flamed and 
cooled scalpel. Lot III was inoculated with a pure culture of Diplodia 
gossypii Zim. obtained from Dr. Edgerton; Lot IV was inoculated 
with a pure culture of Diplodia natalensis Pole Evans ; and Lot V was 
inoculated with a pure culture of Lasiodiplodia theohromae (Patt.) 
Griff, and Maubl. {Lasiodiplodia nigra Appel & Laub.). Attempts 
to secure cultures of Diplodiella, Chaetodiplodia and Botryodiplodia 
failed. The results of the above inoculations were all positive. 
Inoculations with Lasiodiplodia tubericola on the sweet potato repro- 
duced the typical Java black rot (figs. 7 and 8) within ten to twenty 
days. The period of incubation was from eight to nine days. The 
same was true for all the other fungi tried out. The gross symptoms 
produced differed so little from the typical Java black rot that it was 
impossible to tell them apart (figs, i and 2). Specimens of sweet 
potatoes inoculated with Diplodia gossypii and Lasiodiplodia theo- 
hromae were submitted to some of our leading mycologists without 
having been told of these inoculations, and they pronounced them 
similar to Lasiodiplodia tubericola. Sweet potatoes inoculated with 
Diplodia natalensis produced symptoms of Java black rot, but the 
fungus failed to form fertile pycnidia. While the gross symptoms 
were practically alike, a closer examination showed some differ- 
ences. When the fungus Lasiodiplodia tubericola is inoculated into 
the sweet potato, the parasite emits from its pycnidia long strings 
of hyalin, one-celled Macrophoma spores, followed by the emission 
of black powdery heaps of dark one-septate spores of the Diplodia 
type (fig. 4) . The fungus Diplodia gossypii on sweet potatoes did not 
emit the whitish strings of Macrophoma spores, but only produced 
black powdery heaps of spores of the Diplodia type. The same was 
true when Lasiodiplodia theobromae was used. 
In shape, color, and measurements the pycnospores from Lasio- 
diplodia tubericola on sweet potato could hardly be distinguished from 
the pycnospores of Diplodia gossypii, and L. theobromae on the same 
host. It is evident that the hyalin one-celled Macrophoma spores of 
Lasiodiplodia tubericola are immature Diplodia spores. These turn 
brown with age and become one-septate, although they are capable of 
germination while young. 
