76 NUT. 



for propagation afforded by growth of Nut bushes to that of Black 

 Currants, it may well be hoped that the infestation will not prove 

 such a disastrous scourge. 



One of the worst cases of infestation of Filberts which I have 

 myself seen was where the bushes appeared to have been neglected for 

 several years, and were overhung by trees ; and also on a hedge where 

 the Nut bushes had been trimmed back so as to have many shoots ; 

 and where they were in a damp locality between a willow ground and 

 a shady lane, I have seen the galls in profusion. 



The attack is very similar to that on the Black Currants, for figure 

 of which see p. 34. The infested buds similarly develop into swelled 

 knob-like form, which may be described as a spherical growth, con- 

 sisting of an abnormal number of bud-scales and abortive leaves, 

 which are thickened in structure, and more or less spriukled with 

 hairs or other excrescences. The progress of the plant injury is also 

 similar to that of the Black Currant attack. The deformity of the 

 infested bud is advanced so far as to be observable early in the spring, 

 and later on the galled buds, having attained their full growth, dry 

 up and perish, and with the growth of the Nut shoots in July and 

 August, a new growth of galled buds commences. 



The life-history of the Mite, or Acarus, which gives rise to the 

 bud-galls, is similar to that of the Black Currant Gall Mite. It belongs 

 to the PkytoptidcB, which differ from the other divisions of the great 

 order of Acarina, of which they are one of the families, in being more 

 or less elongate and cylindrical in shape, and also in possessing 

 throughout their lives only four legs. Propagation is by eggs. After 

 passing under various appellations, including for a while (when con- 

 sidered to be a distinct genus) that of Calycophthora avellana of 

 Amerling, the species is now placed amongst others of the genus 

 Plii/toiitus as Phytoptns avellana of Nalepa, and it may also be referred 

 to as rhijtoptus rermiformis of Vallot, Targioni-Tozzetti, and Nalepa. 

 The deformed growth of the Nut buds was known of by Vallot as long 

 ago as the year 1834. 



The Mites are too small to be distinguished by the naked eye, 

 and, both in shape and size, resemble those of the Black Currant, 

 PJnjtoptKs rihis (of which a much magnified figure is given at p. 34), 

 so greatly, that for all practical purposes this figure is sufficiently 

 descriptive. 



The shape is cylindrical, occasionally spindle-shaped. The females 

 attain a length of 0-21 millimetre, the males of 0'18 millimetre — 

 that is, of twenty-one hundredth, and eighteen hundredth of a milli- 

 metre respectively ; and a millimetre being the twenty-fifth part of an 

 inch, it is obvious that about a fifth part of that measure cannot be 

 clearly distinguished by the naked eye. The fore part of the body is 



