Some Sapi'op/iytic Fungi of Potatoes. G. II. Pethy bridge. 113 



authors* and obtained by them from pustules on tubers and 

 stems evidently does not belong to Hypomyces, but to some 

 species of Fusarium. Hypomyces does not appear to form 

 pustules breaking through the skin of the potato like some 

 species of Fusarium do, and attempts to produce them by pure 

 culture inoculation of both healthy and sterilised tubers with 

 intact skins failed. 



Conidia. The conidia are produced singly at the apex of 

 the conidiophore. When the conidium is ripe it becomes 

 pushed on one side and does not immediately fall oH. As the 

 formation of conidia proceeds, a globule — at first elliptical, 

 then spherical — forms at the tip of the conidiophore. This 

 consists of a mass of conidia held together in a slightly alkaline 

 fluid, just as occurs in some species of Verticillium. Not 

 infrequently neighbouring globules of conidia in a culture 

 touch one another and coalesce, forming thus a much larger 

 globule which is then supported on several coremia. These 

 globules are seen in Fig. 3, Plate IV, and they can just be 

 discerned with the naked eye in Figs. 2 and 4, Plate IV. 



After the first conidium is formed the protoplasmic contents 

 of the conidiophore contract slightly, and a minute, slightly 

 expanded collar remains at the extreme tip. The conidium 

 next arising grows up and becomes seated in this collar, looking 

 in its early stages like an eg^ in a cup. (See Fig. 10, Plate III.) 

 When the conidium has reached its full size separation occurs 

 at its base between its protoplasm and that of the conidiophore 

 and a slight gap is seen. Subsequently the base of the conidium 

 and the slightly contracted contents of the conidiophore each 

 develop a thin wall. Somewhat the same kind of thing was 

 described for Fusarium caeruleum\ and accounts for the 

 development of the foot-like base of the conidium often seen 

 in Hypomyces as well as in several species of Fusarium. 



Typical conidia of Hypomyces Solani are 3-septate, i.e. 4-celled, 

 but forms with less or more septa are not uncommon. The 

 average of many measurements of typical 3-septate forms was 

 found to be 38)^1 x 6-2 fx. Similar measurements for F. Solani 

 were found to be 30 ju, x 5*3 /x so that the conidia of the latter 

 are considerably smaller than those of Hypomyces Solani. 

 Examples of them are shown in Fig. 9, Plate III. On germina- 

 tion the two terminal cells of the conidium invariably produce 

 germ tubes first ; the intermediate ones either later or not at 

 all. In F. Solani the cells of the conidium were observed to 

 germinate more or less simultaneously. 



* Loc. cit. PI. I, Figs. 5 and 6. 



f Pethybridge and Lafferty. Sci. Proc. Roy. Dublin Soc. xv. (N.S.), No. 21, 

 1917, p. 204. 



