Johnson — Willow Canker. 157 



that Westendorp was right in placing the fungus in the genus 

 Diplodina, in which the conidia are uniseptate, or bisporous and 

 colourless, and not, as Kicks does, in Diplodia, in which the 

 conidia are brown. Possibly, as Kickx himself suggests may be 

 the case, he was examining unripe material, before the cross- wall 

 had had time to form. 



In the case of the Irish canker, in the unripe pycnidium the 

 conidia are bisporous or uniseptate ; and, had they remained so 

 when ripe, the name Diplodina salicicola might have been used ; 

 but when quite ripe, the conidia are, as shown in Plate XIII,, fig. 4, 

 triseptate or tetrasporous. Hence the name Diplodina cannot be 

 used in its original sense to indicate Diplodia-like fungi with 

 colourless conidia. The name Septoria would seem at first sight 

 more appropriate. 



Septoria is a name given to an enormous number of fungi of 

 the group "Fungi Imperfecti," and characterised by pycnidia 

 containing colourless conidia, with several cross- walls. The species 

 of Septoria are confined for the most part to the leaves of their 

 hosts, causing leaf-spot diseases. Where the conidia are bisporous, 

 and occur in pycnidia, as in Diplodina caslanece, it seems desirable 

 to use the name Diplodina rather than Septoria ; as the name 

 Septoria is given to leaf-parasites chiefly, and to such as have 

 conidia with several cross-walls, I propose to call the fungus here 

 found in the stem-canker, and provided with colourless rod-like 

 conidia having, when ripe, three cross-walls, Tetradia salicicola. 

 The cankers show a second kind of swelling, which is a true peri- 

 thecium (0 - 130 x 0"1 mm.) differing entirely in its contents from 

 the pycnidium just described. In this perithecium (Plate XIV., 

 fig. 2) there rises, from the floor only, a hymenium consisting of 

 clavate asci and filiform paraphyses. Each ascus (Plate XIY., 

 fig. 3) contains eight ascospores, more or less in two rows, i.e. 

 distichously or sub-distichously arranged. 



The ascospores are hyaline, continuous, and oblong, with 

 usually an oil-drop, and often a vacuole at each end, as well as a 

 central nucleus. Often the ascospores look as if bisporous, though 

 staining shows they are really continuous or simple. 



Fortunately I have been able to get the opinion of Saccardo 

 on the fungus, and can thus refer this perithecial stage of the 

 fungus to Tliysalospora gregaria, Sacc, of which the following is a 



