r62 Journal of Agricultural Research voi. iv, no. e 



that the breach created by the nematodes afforded entrance to fungous 

 and microbic enemies. 



It will thus be seen that this Hawaiian species of Tylenchus was found 

 under circumstances conclusively proving its parasitic nature. Every 

 degree of infestation was found in the sugar-cane roots, from those which 

 upon external examination, even with a lens, appeared to be in a sound 

 condition to roots spotted with numerous dark infested areas, each har- 

 boring scores of the nematode parasites. Sections of the roots showed 

 that the cavities inhabited by the nematodes were colored or blackened 

 on the inside and that it was this discoloration which gave rise to the 

 outward appearances already described. All stages of the nematode 

 were found in the cavities, including full-grown males and females, and 

 it was plain that this species of Tylenchus lived generation after genera- 

 tion largely in the roots of the sugar cane, though it would undoubtedly 

 be necessary, in the natural course of events, for the progeny sooner or 

 later to remove from one root to another or from one plant to another. 

 It was therefore to be expected that nematodes of this species would be 

 found in soil adjacent to the roots of sugar cane, although the investi- 

 gations made at the time did not disclose any stage of the parasite living 

 free in the soil. 



OCCURRENCE OF TYLENCHUS SIMILIS IN JAMAICA 



Recently this nematode disease has been reported from the Island 

 of Jamaica. The following are extracts from letters written by Mr. S. F. 

 Ashbv, Microbiologist of the Department of Agriculture, Jamaica: 



I send you in a carton some fragments of diseased portions of rhizomes and true 

 stems of the Jamaica (Gros Michel) banana preserved in dilute formalin. The disease, 

 locally called "black head," shows as a black rot working into the tissue from the 

 surface usually from around the insertions of diseased roots; the roots when attacked 

 show depressed dark flocks at the surface, and within the cortex a purple rot disin- 

 tegrating in the older parts. 



The disease is widespread here owing to suckers for planting being frequently dug 

 from affected stools; it is responsible for much backward growth and short bunches 

 on land depending on rainfall in moderate or bad seasons. 



Dr. Erwin F. Smith, after an examination of the material accompany- 

 ing ]\Ir. Ashby's letter, was of the opinion that the disease was not 

 caused by Fusarium spp. 



DESCRIPTION OF TYLENCHUS SIMILIS ^ 



A comparison of the species of Tylenchus found in Hawaii with the 

 other species known at the time seemed to indicate that it was not iden- 

 tical with any form previously described. It was, however, pointed 



1 For an explanation of theformula used in descriptions of nematodes see Cobb, N. A., Antarctic Marine 

 Free-Living Nematodes of the Shackelton Expedition, p. 6, Baltimore, 1914 (Contrib. Sci. Nema- 

 tology, I). 



The illustrations were prepared luider the author's personal supervision by Mr. W. E. Chambers. 



