102 



these animals, in spite of their numbers, have nothing to do with' 

 the cause of the disease, their presence being exclusively a resulting 

 cod sequence. 



Microscopic examinations of the roots with the knobbed appearance 

 shewed the presence of so-called egg-sacs. To one acquaint d with tie 

 history of parasitic woims, this fact in itself is sufficient evidence that 1 

 a species of Nematode was present. The so-called egg-sacs are full- 

 grown ft males, whose bodies are so strangely swollen as to attain a 

 sac or pear shape and are thus quite incapable of locomotion. Inside 

 the motionless sac the ova of the worm are found in different stages of 

 development. Of this genus (Hetercdera) three species have hitherto 

 been known. One of them, H. Schacti (Schmidt), lives on Sugar-beet, 

 having some twenty years ago caused great damage to the beet crop of 

 Germany; a second, H. exigua (JMeloidogyne exigua, Goldi), infests the 

 roots of the Coffee plant, having caused great havoc during the years 

 1885-1888, completely destroying plantations in large districts in 

 Brazil. The history of the latter is very interesting and instructive, 

 inasmuch as the disease could be traced back to 1869 : that is to say, 

 sixteen years before the outbreak became really serious. Nothing was 

 known of ihe pest, nor were any attempts made to cope with it, until 

 tie } ear 1887, when an area of about 715,000 feddans was infected 

 and the cultivation of Coffee rendered impossible. The similarity to 

 the present case is striking. It has been known for seme three or 

 four years that a Banana disease existed in the district around Alex- 

 andria. The disease was first located in a small area, and finally has 

 now spread in the whole neighbourhood, not only infecting planta- 

 tions, but haviDg found its way into private gardens. 



The third species known, H. radicicola (Miiller), is the most interest- 

 ing because it is known to attack the roots of Bananas. About 1880 

 some specimens of Musa Lacca and Musa rosacea, cultivated in the 

 botanic gardens of the University of Berlin, showed sign of disease 

 and it was decided to transplant them. During this process, the 

 strange knobbed appearance of the finer roots was noticed, and micro- 

 scopic examinations showed the worms to be present, and their evolu- 

 tions were studied. It appeared that the ova contained in the egg- 

 sacs or cysts in the adult and immobile females, after having developed 

 and left their egg-shells, escape from their parent. The latter then 

 gradually dies. The worms then make their way through the tissues 

 of the root and enter the soil. They wander about here for some time, 

 growing slowly until they find another root into which they enter, thus 

 transferring the disease from one root to another. Once within a new 

 root they grow rapidly to sexual maturity, and after impregnation the 

 female develops into the original egg-sac or cyst. Such is the life- 

 history of E. radicicola, and by analogy it is extremely probable that 

 the species of Heterodera infecting Egyptian Bananas is very similar, 

 although tl e species itse f is not H. radicicola. This latter possesses 

 within i s mouth-cavity a very fine, sharp protrusive boring dart,- 

 which apparently serves to pierce the walls of the tissue of ihe root 

 and thus faciliate the entrance of the worms. In the species found in 

 Egyptian plants this is wanting, thus indicating that the species i» 

 not identical. 



In the case of the disease found in Alexandria matters are compli- 



