Pethybridge and Laffkrty — Dry-Rot of the Potato Tuber, 221 



V. — Explanation of Plates. 



Plate VI. 



Fig. 



1. A tuber naturally infected with Fusarium cceruleum at a comparatively 



early stage of dry-rot, showing the characteristic shrinking and 

 wrinkling of the skin over the affected portion, and the white 

 eonidia-bearing pustules of the fungus breaking through. (Decem- 

 ber, 1916.) 



2. A naturally infected tuber in the last stages of dry-rot. Having been 



exposed in a window to a good light, the numerous fungus pustules 

 were pinkish in colour. The tuber was much shrunken, dry, light 

 in weight, and very hard. Infection, in all probability, occurred at 

 the wound visible in the centre. (April, 1916.) 



3. Four tubers artificially inoculated through wounds with a pure culture 



of F. cceruleum. In the case of the two upper tubers the rot had 

 been in progress for nine, and in the lower two for four and a half, 

 weeks at the time when the photograph was taken. (November, 

 1914.) 



4. Four tubers ten weeks after being inoculated with a pure culture of 



F. cceruleum by applying it to the skins after scratching them. 

 (January, 1915.) 



5. The two halves of a tuber five weeks after having been inoculated 



with F. arthrosporioides through two wounds on the upper surface, 

 one near each end. (March, 1916.) 



Plate VII. 



1. A branched conidiophore of F. cceruleum, from a 26-days old culture on 

 Quaker Oat agar, showing the " collar " at the extremity of each 

 sterigma except the one on the left to which a young conidium 

 is attached, (x 500.) 



SCIENT. PBOC. K.D.S., VOL. XV., NO. XXI. 2 N 



