68 Pink Disease of Plantation Rubber 



different times of the year. Great difficulty was experienced in finding 

 basidia at all and it was not until after much searching that we recognised 

 the type of incrustation that produced basidiospores. This form is 

 thicker, has a more homogeneous surface, and when dry cracks into 

 larger pieces than the sterile incrustation. It is remarkable that 

 neither Zimmermann nor any other writer has called attention to the 

 fact that the pink incrustation is frequently sterile. 



One concludes from Zimmermann's description and figures that a 

 typical hymenium is developed, but according to our experience the 

 basidia are scattered and are irregularly arranged as in Fig. 6. The size 

 of the spores is as given by Zimmermann and the sterigmata are notice- 

 ably long. We have not seen the basidia arranged even approximately 

 as they are in Zimmermann's figure. The irregular distribution of 

 basidia reminds one rather of an Hypochnus than a Corticium. Rant (10) 

 has apparently made no special study of the basidial stage as he copies 

 Zimmermann's figure of the hymenium and agrees with his description 

 of it. 



In North America, Stevens and Hall (16) have described a disease 

 of pomaceous fruit trees caused by Hypochnus ochroleucus, Noack, 

 which spreads over branches and twigs by means of mycelial strands 

 and kills the leaves by enveloping them. The basidia are scattered 

 and are irregular in form. Corticium salmonicolor seems to be more 

 closely related to Hypochnus ochroleucus than to other species of 

 Corticium. Bernard (3) also has described a disease of tea in Java 

 which he attributes to a fungus named by him Hypochnus theae. Though 

 there appear to be certain minor differences between this fungus and 

 Corticium salmonicolor, the resemblances in the arrangement of the 

 basidia and the character of the sterigmata and spores are very striking. 



(6) Necator stage. The genus Necator was founded by Massee (8) 

 in 1897 for the reception of a single species, Necator decretus, which was 

 the cause of a stem disease of coffee in Malaya. It is now known that 

 this is one of the stages of Corticium salmonicolor. The Necator stage 

 consists of orange-red masses of spores, the individual spores being 

 irregular in shape (Fig. 7) and hyaline when seen under the microscope. 

 Each spore mass is waxy in consistency and it is likely that the spores 

 become separated from one another only in wet weather when they are 

 washed apart. 



The mode of formation of these pustules is different from what 

 one would gather by examining Zimmermann's figures, which have 

 also been reproduced in Rant's paper (10). Zimmermann's figures 



