Some Saprophytic Fungi of Potatoes. G. H. Pethyhridge. 119 



EXPLANATION OF PLATES. 

 Plate IIL 



(All figures were drawn with the aid of a Zeiss Camera 

 Lucida.) 

 Fig. 



1. Unripe (single-celled) and ripe (two-celled) ascospores of 



Nectria inveiifa. x 547. 



2. Ascospores of A^". inventa in various stages of germination 



in tap water, x 547. 



3. An ascospore (a) of N. inventa, the germination and sub- 



sequent development of which on a cover-glass film was 

 followed uninterruptedly under the microscope. The 

 hypha h, h was continuous and developed on the left a 

 characteristic conidiophore bearing conidia of Verti- 

 cillium cinnabar inum. x 333. 



4. Vertical section through a perithecium of N . inventa on 



its stroma. The section is not quite median and 

 therefore does not pass through the ostiole, although 

 the near presence of the latter is seen from the arrange- 

 ment of the cells at the top. For the sake of clearness 

 a large portion of the contents of the perithecium has 

 been omitted. In an actual section the paraphyses 

 are not nearly so clearly defined as is shown, owing to 

 crowding. The mycelium permeating the cork-cells of 

 the skin ot the tuber on which the stroma sits, although 

 present in the section, has been omitted from the 

 drawing, x 55. 



5. Portion of the contents of a perithecium of N. inventa 



teased out, showing the asci and septate paraphyses 

 with rather swollen bases, x 340. 



6. Young " sclerotium " (acervulus) of Colletotrichum tahificum 



on a potato stalk. The long black setae have penetrated 

 through the epidermis but the remainder is still sub- 

 merged in the tissue, x 91. 



7. Appressoria of C. tahificum as developed in pure culture. 



X 560. 



8. Vertical section through the acervulus of C. tahificum, as 



developed in pure culture. Four ripe conidia are shown 

 isolated. The upper surface consists of a palisade-like 

 layer of septate conidiophores, and the basal portions 

 of two setae are shown. The lower part consists of 

 rather thin walled pseudo-parenchymatous tissue, x 340. 



9. Typical conidia of Hypomyccs Solani from a 30-day old 



culture on oat extract agar, x 560. 



