juiyio,i 5 i6 Storage-Rots of Economic Avoids 553 



cola from sweet potatoes and from dasheens and to agree closely in cul- 

 tural characteristics and in shape (fig. 1, C) and size of spores. While 

 Diplodia sp. from Mangijera indica and D. maclurae both produce a 

 typical rot of dasheens and agree with the other species in cultural 

 characteristics and shape of the spores (fig. 1, D, E), the spores of the 

 latter fungus are uniformly smaller in size. D. maclurae is less virulent 

 for dasheens than the other species. The spores from the host of the 

 different species studied measure as follows: 



Diplodia tubericola from sweet potato, 22.3 to 34.4 by 10.3 to 13. 7m- Aver- 

 age, 11. 6 by 25. 5^ (30 measurements). 



Diplodia tubericola from dasheen, 22 to ^3 by 10.3 to 13. 7m. Average, 11. 3 

 by 26. 5m (30 measurements). 



Diplodia gossypina from cotton, 20.1 to 28" by 9 to 13.4/*- Average, 11. 5 by 

 24. 5m (31 measurements). 



Diplodia maclurae from Toxylon pomiferum, 17.5 to 22.3 by 8.5 to iim. Aver- 

 age, 9.7 by 19. 7m (30 measurements). 



Diplodia sp. from Mangijera indica, 23 to 31.6 by 12 to 14. im. Average, 13 by 

 26.2M (31 measurements). 



In 1906 Charles (2) isolated and studied a species of Lasiodiplodia 

 from the fruit of Mangifera indica, but left the question unsettled as 

 to whether it w T as the same organism found on the sweet potato. How- 

 ever, the results obtained by the writer by inoculation studies with the 

 above species and by Taubenhaus (9), who obtained positive infections 

 of sweet potatoes with several species of Diplodia, suggest the possible 

 identity of many of these forms described as different species. The 

 results also indicate that these crops are exposed to infection from sev- 

 eral sources. 



INOCULATION EXPERIMENTS 

 INOCULATION OP COLOCASIA ESCULENTA 



On January 6, 19 14, thirteen dasheen tubers, after being thoroughly 

 washed and disinfected for 10 minutes in mercuric chlorid (1 : 1,000) and 

 rinsed in water, were inoculated in a wound at the end by inserting 

 spores and hyphae of D. tubericola from dasheen. All inoculations were 

 made from cultures grown on cooked potato cylinders in which spores 

 were present, although in many cases they were hyalin and nonseptate. 

 After inoculation the tubers were placed in a large, uncovered, moist 

 chamber and subjected to the temperature and humidity of the labora- 

 tory room. By January 19 the rot had noticeably started on all the 

 tubers, and by January 28 all were completely decayed. The causal 

 organism was recovered in pure culture from each tuber. The checks, 

 six in number, similarly located remained healthy. 



On the same date seven tubers prepared as above and inoculated with 

 the same organism were placed in a covered moist chamber with wet 

 filter paper in the bottom and placed on a shelf in the laboratory. These 



