De structuur van de kegeltop als taxonomisch kenmerk bij heterodera-soorten met citroenvormige cysten

Summary Referring to an earlier communication of the authors additional data are furnished on the taxonomical value of the structure of the vulva cone in lemonshapedHeterodera cysts (figs 1–5, table 1).InH. avenae=H. major the transparent lip tops of the cone are narrow and have a very short touching line, forming together the shape of an 8. The vulvar split is extremely short, probably too short to enable the deposition of eggs in the gelatinous egg sac around the cyst vulva which phenomenon normally occurs in other lemon-shapedHeterodera-species. These characters are useful, in addition to others, to separateH. avenae from mixed populations. H. schachtii shows smaller transperent patches on the lip tops thanH. trifolii and this character is probably useful for separating these species in practical advisory work. The average length of the patches (1 in the drawing of table 1) proved to be 32,1 and 45,6 . An average of 5 specimens is adequate to place a population below or above 38.7 , which is the limiting value between the two species, according to statistical treatment of the presented data.