PYRENOMYCETES 



[CH. 



142 



Lachnea cretea and the Ascoboli, where the coiled and septate archicarp is 



often still functional. 



A very common initial organ in forms with embedded perithecia is the 

 short filament of cells sometimes known as Woronin's hypha (fig. 103). The 

 cells are large and contain well-marked nuclei and lie in a nest of small- 

 celled vegetative mycelium. Woronin's hypha has been found among the 

 Hypocreales mNectria and among the Sphaeriales in Xylaria zn&Hypoxylon ; 



it remains to be shown whether 

 it still functions. It may have 

 originated from the simple archi- 

 carps of the Lower Pyrenomy- 

 cetes or by reduction from forms 

 with a multicellular trichogyne. 

 With its final disappearance we 

 reach such completely apogamous 

 species as those of Cordyceps and 

 Claviceps. 



(iii) A quite distinct type of 

 primordium has been described 

 in Strickeria, Sporormia and Pleo- 

 spora; in these cases the asco- 

 genous and vegetative filaments 

 arise from a common initial cell 

 which divides not only transverse- 

 ly, but longitudinally, forming a 

 compact tissue (fig. 104). Other hyphae may anastomose with this mass, 

 or it may give rise alone to the whole fructification. Possibly some sugges- 

 tion of its origin may be found in the peculiar, but apparently normally 

 fertilized oogonium of Leptosphaeria. 



The Pyrenomycetes do not appear to have given rise to any higher 

 forms, and have themselves a greater vegetative development than any other 

 Ascomycetes. 



They may be subdivided as follows : 



Wall of perithecium differentiated from stroma; 



perithecium wall and stroma, if present, soft in 

 texture, either colourless or light coloured 



Fig. 104. Strickeria sp.; initial cells of ascocarps ; 

 after Nichols. 



perithecium wall and stroma, if present, firm, leathery 



or brittle, dark in colour 

 Perithecium always sunk in a stroma from the tissue of 



which its wall is not differentiated ; colour of stroma 



black or dark brown 

 Minute, external parasites on insects, perithecium borne 



on a receptacle which also bears appendages; spores 



two-celled 



HYPOCREALES. 



SPHAERIALES. 



DOTHIDEALES. 



LABOULBENIALES 



