178 PETCH : 



The stromata are, in general, white, or brightly coloured 

 in various shades of yellow, red, or brown. Hypocrella 

 bispora is rather an exception, the specimens available being 

 purple-brown or purple-black. In many species the colour 

 is not constant, e.g., H. mollii may be either white or pale 

 yellow, H. discoidea orange-red or yellow, &c. The colouration 

 often extends from the exterior to a depth of about '25 mm., 

 forming a distinct peripheral zone ; this is well marked in 

 ascigerous examples of H. olivacea and H. palmicola, and in 

 the Aschersonia stage of H. javanica. As a rule, the colour 

 is soluble in alcohol, and hence specimens preserved in alcohol 

 are usually bleached. 



Sections of the stromata treated with caustic potash change 

 colour or give a coloured extract. Notes on these changes are 

 given in the descriptions of the species. Hypocrella olivacea 

 usually yields a yellow-brown extract, and Hypocrella javanica 

 and Hypocrella ceramichroa a purple extract or colouration. 

 But in other species this effect may vary with the condition 

 of the stroma, as it does in many tropical species of Hypoxylon. 

 In H. Reineckiana some specimens do not change colour, 

 others may yield a yellow-brown extract from the perithecia, 

 while others turn purple in patches. These changes are most 

 evident in the Lecaniicolous species. In the case of the 

 species parasitic on Aleyrodidee, the colour changes with 

 potash are usually shght, though the presence of a minute 

 fragment of the insect may induce a totally different result ; 

 a black Aleyrodes, which is commonly attacked by these fungi 

 in Ceylon, yields a vivid colour with potash. 



Apparently most species, but especially those parasitic 

 on Lecaniidie, turn black when old, independently of the 

 growth of Meliola, &c., over them. And in this connection 

 age is to be taken in its literal sense, not as indicating that the 

 stroma has ripened its spores. Blackened stromata may be 

 quite immature, the development of such having probably 

 been arrested by adverse weather conditions. Many of the 

 pale-coloured Aleyrodiicolous species turn green, especially 

 round or in the ostiola ; the cause of this has not been ascer- 

 tained. In some specimens of Hypocrella Mollii, collected in 

 Ceylon, the ostiola are green on one half of the stroma, and 



