Jfew South Wales. 181 



the trap-roots. Mangels will make the best trap-root, and they should be 

 sown thickly. 



2. Oall-proof Varieties. — Dr. Ncal recommends, as a practically gall-proof 

 stock for the orange, the hardy bitter-sweet or 60ur species, and, with some 

 qualification, Citrus trifoliata, and the Japanese Unshin, or iSatsuma ; as a 

 neai'ly gall-proof stock for the peacli, seedling American wild plum or one 

 of the Japanese plums Kelsey, Satsuma, or Ogru ; as a stock for grapes 

 perhaps the cordiJoUa or vtilpina races. Por other plants subject to root- 

 gall he found no resistant stocks. 



Fire la a powerful destructive agent which may, in certain case."*, be 

 brought into play in combating root-gall. Tlie larva; of the gail-worm infest 

 the soil to a depth of at least 2 feet, but by far the greater number are 

 found within a few inches of the surface. The heat of a large fire will 

 penetrate to this depth in sufficient degree to destroy life. This fact may 

 be applied iu setting out tliose trees particularly subject to root-gall, such as 

 the peach, apricot, almond, plum, and fig. Nothing short of a large fire, 

 lasting several hours, will kill the worms. The tree must be set in the midst 

 of the burnt area, and no soil or fertilizer used except such as is known to 

 be free from gall-worms. 



3. Use of destructive c7tfi7«/c«/s.-*-K.\periment,s looking towards the use o£ 

 some fertilizer or chemical destructive to gall-worms have been made, and 

 the results may bo summed up as on the whole negative. No thorough- 

 going chemical remedy for Eiibenmiidigkeifc has ever been discovered, 

 although multitudes have been tried. Similar negative results were obtained 

 by Dr. Ncal in the case of T. arenarius. Still the results are interesting, as 

 pointing out what positively will not succeed ; furthermore, they may bo 

 made the basis of plans for further trials. 



Of all the vermicides yet tried, lime receives the highest commendation. 

 It must bo used iu large quantities to be effective. (The same is true of the 

 muriates and sulphates of potash and ammonium.) One to two tons of lime 

 to the acre, applied, not all at once, but part in Juno and the remainder in 

 October or November, may be recommended. The result is the destruction 

 of a large number of worms ; but many eggs, protected bythctissues in which 

 they are being incubated, doubtless escape destruction, and live to propagate 

 the disease. I have noticed that when the disease is combated with 

 chemicals, the method has been in all eases drastic, the attempt being to kill 

 all the worms at one fell swoop. Possibly a homoeopathic treatment would 

 be more fatal. It is easy to believe that many of tlie experiments which 

 have been tried were in reality effective so far as they went, although 

 pronounced unsuccessful because the disease reappeared. My experiments 

 have already shown that the period occupied by the development of the egg 

 of T. arenarius may possibly extend over two months or more. While yet 

 in the egg, the young worm is protected by the shell ; and this protection is 

 a good one. The shells of nematode eggs (as well as tlie skin of the larva when 

 it is being cast) are comparatively impenetrable. Poisons which would at 

 other stages of life be fatal, can therefore be withstood by embryos and 

 moulting larva;. I may support those statements, which are based on my own 

 observations and experiments,* by the remark that the eggs develop in the very 

 midst of decaying matter. The roots attacked by the disease die and decay, 

 thus giving rise to chemicnls of considerable strength and acti^^ty. Yet the 

 eggs develop unharmed — quite likely, on account of the impenetrability of 

 their shells. Now, suppose in some of the numerous experiments that have 



• For instance, 1 have observed that spcrios which under ordinary circumst.incca are instantly l<llled 

 by osmic acid may withstand the acid for an liour wlien moultin);. 



