^ew South Wales. 157 



Pretty Q-ully Scrub. Its appearance is not easily described. Ifc was com- 

 pletely covered with knobs, some smooth, others rough and warty. These 

 knobs varied from the size of a pin's head to that of a beau. When smooth, 

 as were moat of the smaller knobs, they had a water-soaked appearance, and 

 cutting them only confinned the impression gained from outward inspection. 

 It is this water-soaked appearance which sometimes gives to the smoother 

 knobs the aspect of blisters. The potato shown in the figure weighed 

 2J ounces, and I estimated it to contain upwards of 10,000 mature, or 

 nearly mature, worms, and a much larger number of younger worms and 

 innumerable eggs. 



The only other roots forwarded from Pretty Gully were those of the 

 peach-tree. The a])pearance of the disease as manifested in peach-tree 

 roots is also sliown by the plate. 



From what I have learned of the habits of similar parasites, I suspect that 

 the Pretty Gully Scrub worm will be found, upon more careful search, to 

 infest, to a greater or less extent, nearly every cultivated plant and many 

 wild ones. 



Methods of Examining. 



In searching for the worms, not all root.^ are equally easy to examine. The 

 tissues of the parsnip, for example, are so tough that as a rule many worms 

 will be mutilated in the endeavour to extract them. The same is true, to a 

 certain extent, of peach-tree roots. The tissues of potato yield up the worms 

 moi-e readily. The method used most successfully in extracting both mature 

 and young worms, was the following : — Cut from the potato slices one-eighth 

 of au inch thick, and place them in water in a shallow glass dish. On examining 

 with a magnifying glass the mature worms will appear as white sacs of the 

 size of a pin's head. If the worms are numerous, some of them will be seen 

 to have been cut in two, giving rise thereby to a miikiness. Search for one 

 which remains uninjured, and, using transmitted light, cut it away from the 

 slice in a cube of the tissue just large enough to contain it. The operation 

 should be performed with a small sharp knife. The cube will be sulHcientlv 

 ti'anslucent to give a rather indefinite view of the worm. Now with a pair 

 of exceedingly sharp needles gradually and carefully remove the tissue bit 

 by bit. Mxev some minutes, if no slip be made, the worm will fall out from 

 the cavity which contained it. Any slip or the slightest pressure will burst 

 the worm and render it comparatively worthless for purposes of examination. 

 The worms first removed will probably have the form shown in II, Fig. 1, 

 on the following page, and it is to the structure of this form that we will 

 turn our attention, after first noting the methods by wliich we shall obtain 

 the best results. 



For immediate examination the worm is best placed in -iV per cent, osmic 

 acid. Examination in water is much less satisfactory. The best method of 

 all is to kill at once in warm concentrated solution of corrosive sublinuite, 

 and then bring the specimen, by means of the differentiator, into balsam, 

 after having stained with Mayer's carmine. Borax carmine docs not pene- 

 trate the cuticle sufficiently to stain the tissue, at least in a reasonable 

 length of time. The examination, which of course is microscopic, must be 

 conducted by mounting the worm on an object glass under a cover-slip, 

 8U])ported by two pieces of bristle. The pieces of bristle, or whatever other 

 objects be substituted for them, should have a diameter barely less than that 

 of the worm itself. This permits the cover-slip to press very sliijlilh/ on the 

 worm, and it will be found that by moving the cover the worm can be rolled 

 into any desired position. 



