SPHAERIALES 285 



The species of Cryptosporella and Cryptospora are characterized by 

 unicellular ascospores and by a conical ectostromatic disc about which the 

 perithecia are arranged circinately with the unaltered bark cortex. 

 There is no differentiated entostromatic area nor dark marginal zone. 

 The imperfect stages have been placed in Fusicoccum and Disculina 

 (Cryptosporium) . The fructifications consist of an ectostromatic cushion 

 which contains open cavities or enclosed locules, usually on the marginal 

 portions of the ectostroma. The conidia are unicellular, hyaline and more 

 or less elongate. These characters show a relationship to Melanconis. 



The third series includes Valsa, Leucostoma, Valsella, Endothia and 

 Valsaria. In Valsa the structure is quite simple and resembles that of 

 Melanconis, but in the other genera there is a well-developed and strongly 

 differentiated entostroma. Ascospores, except in some species of Endothia 

 and Valsaria, are allantoid, hyaline and unicellular. The conidial 

 chambers are numerous or labyrinthiform and produced both in ento- 

 stroma and ectostroma. Glomerella, with its allantoid ascospores, 

 presents a possible origin for this series among the simple Sphaeriales. 

 There seems to be a wide gap between such forms and the species of 

 Valsa. 



The species of Valsa have a definitely differentiated truncate conical 

 ectostroma which forms the erumpent disc. The perithecia are buried 

 in the bark cortex beneath this ectostroma. The entostroma is very 

 slightly developed and visible only under a microscope, while the ecto- 

 stroma is sharply defined. The imperfect stage belongs to the form genus 

 Cytospora. The fructifications consist of an entostroma containing 

 numerous locules which often coalesce into a labyrinthiform chamber. 

 The conidia are small, allantoid, unicellular, hyaline and ejected in large 

 numbers in the form of a spore horn. 



In Leucostoma, the differentiation between ectostroma and entostroma 

 is vague. In some species, as Leucostoma subclypeata (Valsa subclypeata) , 

 there is formed a differentiated cap of ectostromatic mycelium. In all 

 species the stromatic area is delimited very early in its development by 

 a dark marginal zone of tissue which limits the size of the stroma. In 

 Leucostoma Persoonii (Valsa leucostoma), the dieback of stone fruits, this 

 zone runs just beneath the periderm and the stroma develops between 

 the periderm and the bark surface. In Leucostoma subclypeata, this 

 blackened zone may penetrate into the bark, cutting off a spherical area 

 within which the bark cells are absorbed and replaced by a stromatic 

 fungous tissue. Where there is formed a differentiated cap of tissue 

 which opens the periderm, the stromatic tissue, in which the perithecia 

 are imbedded, should undoubtedly be considered as entostroma. In 

 many cases this tissue develops entirely upon the bark surface. 



Valsella differs only in its polysporous asci. Endothia is also close to 

 Leucostoma. In E. parasitica (Fig. 186) the stroma usually arises as a 



