GENEEA HYPOCRELLA AND ASCHERSONIA. 537 



Hypocrella discoidea and the fiist five species of Aschersonia 

 are, typically, discoid, i.e., circular, flattened discs with a 

 more or less abrupt margin (neglecting the hypothallus when 

 present), and would, at first sight, appear to form a natural 

 group. But those of which a large amount of material is 

 available, e.g., H. discoidea, are found to occur in inegularly 

 pulvinate form also, and thus resemble H. mollii, whicli may 

 be described as ejffused pulvinate. In these species the 

 perithecia and pycnidia are regularly flask-shaped or almost 

 globose, with definite ostiola. 



• Aschersonia placenta, A. aleyrodis, A. zenkeri, A. Goldiana, 

 A. Tamurai form a grouj) in which the pycnidia are irregular 

 and ultimately widely open, so that the extruded conidia fuse 

 into a continuous mass which usually covers the centre of 

 the stroma. A. tahitensis is intermediate (in shape) between 

 A. placenta and A. samoensis ; it has the discoid stroma 

 of the latter and the irregular pycnidial orifices of the 

 former. 



In Hypocrella sloanese and H. Raciborskii, the conidial 

 stage, when present, occupies the centre of the stroma, the 

 perithecia being developed marginaUy. As the perithecia 

 are usually distinct, these are botryose forms, parallel to //. 

 amomi. The extent to which this botryose character may be 

 developed is illustrated bj^ the assignment of //. Raciborskii 

 to the genus Barya. 



It may be noted that, \Wth one possible exception, the 

 species of the Eastern Hemisphere are distinct from those of 

 the Western. Closely aUied species occur in the two regions 

 respectively, e.g., Hypocrella pulmse and H. marginata, H. 

 epiphylla and H. Reineckiana, Aschersonia aleyrodis and A. 

 placenta, but they are sufficiently different to be maintained 

 as distinct species. 



The only exception to this rule, at present, is Hypocrella 

 camerunensis, which is recorded from Brazil and Africa. Tiu' 

 stromata of the Brazihan and Afiican collections difier 

 considerably in shape, but the variation is not greater than 

 that which is known to occur in Hypocrella marginata. 

 Unfortunately in none of the collections yet made arc the 

 stromata mature. 



6(4)14 (60) 



