208 



THE ASCOMYCETES 



Another member of special interest is Pleosphaeria citri, oc- 

 curring on citrus and oleander in the Mediterranean area. It is 

 epiphytic, subsisting on the honey dew of plant Uce. Both peri- 

 thecial and pycnidial stages are embedded in a thin but well- 

 defined, loosely woven stroma. 



LoPHiosTOMATACEAE. As the name of this family indicates, the 

 perithecial ostioles of its members are laterally compressed and 



have slit-like openings. For 

 this reason the Lophiostomata- 

 ceae are regarded as a link 

 connecting the Sphaeriales 

 with the Hysteriales. All of 

 them seem to be saprophytic 

 on herbaceous or woody 

 stems. No detailed studies of 

 any of them appear to have 

 been made. 



Mycosphaerellaceae. This 

 family is beyond all doubt the 

 most unwieldy assemblage of 

 Pyrenomycetes. As employed 

 in this book, it includes the 

 Pleosporaceae, as used by Lin- 

 FiG. 77. Caryospora putaminiim. A. dau, excepting those members 

 Half of peach pit, at the surface of belonging to the Pseudosphae- 

 which are numerous black perithecia. riaceae, which were included 

 B. Perithecium, in oudine, indicating ^^ ^^^ Myriangiales. The 

 shape and attachment to the pit. C. ^. ' • • r 



A/r 11 J r.1 ,,.,vi, Pleosporaceae remaming arter 



Mature two-celled ascospore with ^ r & 



thick envelope. D. Typical ascus. this arrangement resemble 



Mycosphaerellaceae in all fea- 

 tures except that they possess paraphyses. Such a characteristic 

 seems scarcely worthy to constitute a basis for familial rank. 

 In the Mycosphaerellaceae the genera Mycosphaerella, Guignardia, 

 Venturia, Physalospora, and Ophiobolus deserve attention, partly 

 for the reason that they contain so many plant pathogens, some 

 of which are very destructive to crop plants. 



Mycosphaerella. Mycosphaerella, as at present delimited, 

 contains well over 1000 species. Many of them possess a conidial 

 stage that has been classified as belonging to such form genera 

 as Phyllosticta, Phoma, Ascochyta, Septoria, Phleospora, Ramu- 



