An Electron Microscope Study of Cysts in the Saprolegniaceae

The structure of the zoospore cysts of various members of theSaprolegniaceae has been studied by electron microscopy. InSaprolegnia ferax, S. dioica, in Isoachlya eccentrica and I.unispora the primary cysts were smooth, whilst the secondarycysts bore stalked double-headed hooks. In S. parasitica thesecondary cysts bore tufts of longer hooks. In Protoachlya,Achlya, and Brevilegnia neither type of cyst bore hooks. InDictyuchus sterile the secondary cysts bore large spiny projections.The primary cysts in many species bore tufts of radiating hairs,and it is suggested that these are the remains of ciliated flagella.