A. M. Taylor 251 



of the leaves which bear them, and it is therefore these outgrowths 

 which are in actual contact with the inner smooth surface of the 

 enfolding leaves. The spaces thus formed between the glands, allow 

 the worms to pass between them, and though the glands never appear 

 to be attacked, the interstices are noticeably so. 



Thus the dissected leaves of a diseased bud ^vill, at an early stage 

 of attack, shew a complete reproduction in sharply contrasting colours 

 of the gland-bearing leaf on its opposing glandless leaf. The glands 

 are represented by small bright green circular areas on the glandless 

 leaf — proving that the worms are unable to attack the parts so pro- 

 tected — while the tissues between them are attacked and discoloured 

 by the action of the worms. 



Such evidence therefore leads one to suppose that were the glands 

 absent, and the bud scales more closely appressed, neither worm nor 

 mite could gain entrance between them. 



At this stage of the disease the condition of moisture, associated 

 with which is the transparent appearance of the injured tissues, begins 

 to shew itself. Both symptoms are characteristic of eelworm attack, 

 and are alike caused by the exudation of sap from the injured tissues. 

 The transparent appearance of the attacked portions is invariably 

 present in the initial stage of attack before decay has set in, but the 

 amount of moisture apparently depends on the position of the attacked 

 bud. Thus the terminal buds, always highly developed, shew by their 

 excessive state of moisture under attack, that a higher concentration 

 of sap is present in them than in the lateral buds, which occasionally 

 exude but a negligeable quantity under the same conditions. It is 

 interesting to note that this excess of moisture which is apparently a 

 necessary medium for the nematode, is not one that will support the 

 life of the other inhabitants of the attacked bud, for the mites and 

 their chalcid parasites are often, when sought for microscopically, found 

 to be entirely immersed and drowned in the sap exuded by the leaves. 



The rapidity with which an attacked bud is reduced to a state of 

 decay depends on two factors, (i) the time of year when the buds are 

 attacked, and (ii) the strength of the colony invading them. Thus 

 in the spring of the year when the buds are minute, the rate at which 

 they are destroyed is alarming; later, however, when they are more 

 developed and especially when they are stimulated into abnormal 

 growth by the action of Eriophyes ribis, the decay is not so rapid. 

 Laboratory experiments shewed that from five to six weeks elapsed 

 from the date of inoculation to the death of the fully developed mite- 



Joarn. of Agric. Sci. vin 17 



