63 



constantly proportional to the length of the hypha, but falls off 

 continuously relatively to the length. The extension of branches 

 follows the same process as that of the main hypha, and falls off 

 in rate continuously relatively to the length; but as a rule a 

 branch grows faster than its parent hypha, and in many cases 

 the rate of extension of the total hyphal system (i.e., parent 

 hypha, branches, and sub-branches taken together) is constantly 

 proportional for long periods to the total length. No evidence 

 was found of any actual increase in the growth rate relatively 

 to the amount of substance growing, such as is described in the 

 case of bacteria, nor anything which suggests the formation 

 during the hyphal development of any substance accelerating its 

 growth. 



See also " Fungus Pests and their Control, Wart Disease." 

 Papers No. LVI., LVII. 



V. THE PLANT IN DISEASE; CONTROL OF DISEASE. 



(Entomological, Insecticides and Fungicides, and Mycological 



Departments.) 



(a) INSECT PESTS AND THEIR CONTROL. 



XLVIII. J. G. H. Frew. " On the Larval Anatomy of the 

 Gout-fly of Barley (Chlorops taeniopus Meig.) and two 

 Related Acalyptrate Muscids, with Notes on their 

 Winter Host-Plants.' 1 Proceedings of Zoological 

 Society, London, 1923. No. LIV., pp. 783-821. 



The metamorphosis of the Gout-fly is fully described with a 

 detailed account of the external and internal anatomy of the 

 mature larva. The structure of the larva in its first and second 

 instars is also discussed. Included in this paper are observa- 

 tions on the metamorphosis of Meromyza nigriventris and 

 Balioptera combinata — two little known minor pests of winter 

 barley and wheat. 



The extent to which all three species utilise wild grasses as 

 winter-hosts has also been examined. Chlorops tceniopus has only 

 been found in Agropyrum repens among the wild grasses 

 examined. Meromyza nigriventris occurs in A, repens, Festuca 

 ovina, and Alopecurus pratensis ; Balioptera combinata occurs 

 in A, repens, Festuca elatior, Lolium perenne, Holcus lanatus, 

 and Agrostis alba. The following grasses have also been 

 examined but do not appear to function as winter hosts for any 

 species: — Lolium. italicum, Poa pratensis, P. trivalis, P. annua, 

 Agrostis vulgaris, Alopecurus agrestis, Arrhenatherum avenaceum, 

 Anthoxanthum odoratum, Avena pubescens. Cynosurus cristatus, 

 and Dactylis glomerata. 



XLIX. J. G. H. Frew. " On Chlorops taeniopus Meig." 



(The Gout Fly of Barley.) Annals of Applied Biology, 



1924. Vol. XL, pp. 175-219. 



Chlorops tceniopus passes through two generations per year. 



The winter generation is mainly upon couch grass but also 



occasionally upon winter wheat or upon self-sown wheat or 



