i6o PYRENOMYCETES [CH. 



i 



The type of development here is very similar to that already described 

 for Sporormia; it seems very doubtful whether the initial cell of the peri- 

 thecium should be regarded as an oogonium, or whether the development 

 is purely vegetative. The peculiarity in either case is the formation of the 

 bulk of the perithecium from a single cell instead of, as in the majority of 

 forms, from a complex of interwoven hyphae differentiated into sexual and 

 vegetative components. 



AMPHISPHAERIACEAE : BIBLIOGRAPHY 



1896 Nichols, M. A. The Morphology and Development of certain Pyrenomycetous 

 Fungi. Bot. Gaz. xxii, p. 301. 



L ophiostomataceae 



The perithecia of the Lophiostomataceae are borne singly; during de- 

 velopment they are embedded in the substratum, and they may so remain 

 or may become partially free at maturity. There is no stroma, and the 

 peridium is black and brittle. So far there is a close resemblance to the 

 Amphisphaeriaceae, but the Lophiostomataceae are distinguished by the 

 form of the ostiole, which is very large and laterally compressed, so that in 

 external appearance they approach certain of the Hysteriales which in many 

 cases they further resemble in their habitat on vegetable remains such as 

 wood and bark. None of the species has been investigated in detail. 



Mycosphaerellaceae 



The Mycosphaerellaceae are parasitic forms occurring usually on leaves 

 and giving rise to various kinds of leaf-spot. The perithecia are sunk in the 

 substratum and develop either under the cuticle or beneath the epidermis, 

 breaking through at maturity. The ascospores are usually septate, frequentl}- 

 bicellular and sometimes dark-coloured; except in the transitional genus 

 Stigmatea, paraphyses are not developed. In several cases the formation 

 of the perithecia is preceded by a conidial stage. 



Mycosphaerella nigerristigma forms pycnidia on the living leaves of 

 Pruniis pennsylvanica and perithecia after the leaves have fallen. A tri- 

 chogyne like that of Poly stigma has been recorded ; it degenerates, leaving a 

 basal cell, but whether this functions is not known. 



MYCOSPHAERELLACEAE : BIBLIOGRAPHY 



1914 HiGGlNS, B. B. Life-History of a new species of Sphaerella. Myc. Centralbl. iv, 

 p. 187. 



