CCXxii PROCEEDINGS OF THE ROYAL HORTICULTURAL SOCIETY. 



filled with the remains of blue-bottle-flies on which the grubs had fed. 

 The insects had not utilised the borings of any other insect. The wood 

 no doubt was decayed before the bees attacked it, so that they were in no 

 way the cause of the death of the wood." 



Banana Disease, — Referring to a matter which had been discussed 

 on August 13, the following remarks were communicated by Dr. Axel 

 Preyer : — " For about three years a peculiar disease has been spreading 

 amongst Bananas cultivated near Alexandria. The first symptoms of 

 the disease are to be observed in a sudden check of growth, and soon 

 afterwards the leaf-points and the youngest central leaf become black 

 and die. The latter gets rotten, numerous ants and other small animals 

 inhabit the upper part of the stem, and the putrefaction proceeds 

 downwards. The stem does not die immediately, but it is naturally unfit 

 to bear fruit. Very characteristic is the appearance of a great many 

 small, crippled leaves instead of a few, well-shaped large ones, as is seen 

 in the sound plant. 



" A strongly infected stem dug out of the earth with roots was cut in 

 a longitudinal direction. In the upper part, the youngest leaves were all 

 black and rotten ; the outer layers were white and seemed to be sound, 

 only the fourth and fifth layers were dark brown and saturated with a 

 putrid liquid. The lower part of the stem and the root-stalk showed no 

 sign of disease. But on the roots themselves, especially on the root- 

 tips, one could observe small knobs, generally accompanied by an 

 excretion of a resinous substance. Sections of these knobs were first 

 examined under the microscope, and their contents were found to be 

 relatively large egg-sacs of a kind of pest belonging to the Nematodes. 

 The eggs were in difi'erent stages of development ; even some full-grown 

 Nematodes, possessed with great mobility, had penetrated into the 

 cellular texture of the root. On further investigation, and by comparing 

 infected with uninfected plants, the Nematodes may be stated to be the 

 cause of the Banana disease ; therefore the latter is due to an infection 

 of the roots. 



" The Nematodes themselves are in shape long, thin, and cylindrical, 

 with a round mouth-end and a fine sharp point at the other end, which 

 is strengthened by a thickening of the epidermis. The whole length is 

 0'57 millimetre, the maximum diameter 0*014 mm. The pest belongs 

 to the genus Tylenclius, but its specific identification has not yet been 

 ascertained. This Nematode resembles very much the Tylenclius acuto- 

 caudatus, Zn., which is the cause of a well-known dangerous coffee 

 disease in Java. 



" As to the biology of the Banana Tylenchus, it is an interesting fact 

 that the pest not only lives in the roots, but ascends with the watery 

 liquid streaming upward, and it is to be met with in great numbers in 

 the upper parts of the stem. I could not, however, find any egg-sacs in 

 these parts. 



" The most important question with regard to the Banana disease is, 

 of course, how to suppress it. In this case the task is rather difficult, 

 because the Nematodes live free in the ground, and seem to have spread 

 over a great area near Alexandria. Experiments are going on by 

 manuring the Bananas with nitrates, and by isolating the plantations by 



