846 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



by the presence of at least one other species of parasitic nematode. It 

 has already been stated that the ova of Heterodera are as a rule enclosed 

 in the body of the female parent, the cyst or egg- sac. 



The microscopic examination of the specimens first taken of the roots 

 showed, in both the knobbed and the dotted rootlets, the presence of 

 nematode ova differing in shape and especially in size from those of 

 H. radicicola. They were also irregularly scattered through the tissues 

 of the root, being accumulated in small numbers in some places, in large 

 numbers in others, and sometimes were found in single specimens. It 

 appears that these ova cannot be derived from the pear-shaped and 

 motionless worms, but must belong to a species the adult females of 

 which are wandering freely within the root, depositing their eggs 

 gradually as they wander about. No trace, however, was found of the 

 females themselves ; whereas the larvje already hatched from their eggs, 

 and clearly differing in size and shape from those of the first species 

 {H. radicicola), weve found both within the roots and outside in the earth 

 adhering to their surfaces. 



In the latter case they were sometimes considerable in number, and 

 they showed signs of advanced growth. They were of various sizes, the 

 most advanced showing the first signs of genital organs, preser\'ing, how- 

 ever, at the same time, their original shape, viz. a blunt, almost rounded 

 tail, and a fine sharp dart within the mouth-caWty. From the fact also 

 that no full-grown individuals were discovered in the soil, it appears that 

 they do not exist at the present season (December to January). 



Owing to the absence of full-grown animals, it is impossible to 

 determine the species, though probably it is one hitherto unknown. 

 There can, however, be no doubt that the young worms found in the soil 

 will finally return to the roots to accomplish their development, thus 

 gradually infecting the whole soil, as previously explained. Owing to the 

 numbers in which they exist, it appears that this unknown species plays 

 a far more important role in bringing about the disease in the present 

 case than the species first described. It is also likely that to their 

 presence may be attributed the dying off of the small lateral offshoots of 

 the roots mentioned previously, though the evidence at present available 

 does not permit of a definite opinion. 



It is not improbable that even a third species of nematode is involved 

 in the present Banana disease, for in some instances there were found in 

 the adhering earth, and amongst the larvae of the two forms previously 

 described, young worms, which could not possibly belong to either owing 

 to their shape, but which possessed the fine, sharp protrusive dart in the 

 mouth-cavity. The number present, however, was very limited. Such is 

 the result of microscox3ic examination, from which it seemed to be 

 sufficiently clear that the nematodes are the cause of the disease, and that 

 the second and unknown species described is by far the most injurious. 



The most important question to be considered is how to cope with the 

 disease; in other words, how to prevent the propagation of the worms. 

 This can only be arrived at through an exact knowledge of the life- 

 history of the pests. 



In order to arrive at this an examination at one season of the year will 

 not suffice, and with the advent of warmer weather further observations 



