ORDER SPHAERIALES 277 



spherical and have a small ostiolar papilla. They sit externally on the 

 host with their bases sunk in a more or less well-developed subiculum. 

 The ellipsoidal, colored, one-celled ascospores are eight to each ascus. 

 Filamentous paraphyses are present. Because of the ascospore characters, 

 Vincens (1921), Wehmeyer (1926), and Miller (1928) suggest that this 

 genus belongs more properly near the Xylariaceae. Other genera in the 

 family vary as to color and number of cells in the ascospores as well as to 

 the hairiness of the perithecia. In many genera the asci ripen successively 

 and project one or two at a time from the ostiole to discharge their spores, 

 the emptied asci contracting back into the perithecium and giving place 

 to the next maturing asci. (Fig. 90 E, F.) 



Family Ceratostomataceae. In this family the perithecia have a 

 distinct, sometimes fairly long neck, otherwise much like the Sphaeri- 

 aceae. The perithecial walls are mostly leathery rather than brittle. The 

 asci are mostly accompanied with paraphyses and do not digest as in the 

 next family. The ascospores are one-celled, two-celled, phragmosporous 

 or muriform, and hyaline or brown. The species are mostly saprophytic, 

 growing on wood, bark, or sometimes on stems of herbaceous plants. The 

 genus Ceratostomella, more properly called Ophiostoma, has been segre- 

 gated to form the following family, which is discussed here although 

 Nannfeldt (1932) places it in Order Aspergillales. 



Family Ophiostomataceae. The perithecia have very long necks. 

 In the genus Ophiostoma (Ceratostomella) the neck is often several times as 

 long as the diameter of the perithecium. It has a thin perithecial wall and 

 the roundish asci are scattered throughout the perithecial cavity, without 

 paraphyses. The ascus walls undergo autodigestion and with the absorp- 

 tion of water the resultant gummy mass swells and escapes from the apex 

 of the neck as a hyaline drop containing thousands of the one-celled 

 hyaline spores. Because of these characters Nannfeldt placed this family 

 in the Aspergillales. Several species of Ophiostoma grow on the wood of 

 various trees whose sapwood takes on a blue color, the so-called "sap 

 stain," owing to the presence of the mycelium in the wood cells. The 

 conidial stages of the various species of this genus have been described 

 under a number of names in accordance with the type of conidia and 

 conidiophores. Chalara or Thielaviopsis produce their conidia endoge- 

 nously. In Cephalosporium the conidia are produced externally on separate 



Fig. 90 — (Continued) 



subiculum. (F) Asci, mature and young, and paraphyses. (G) Family Ophiostoma- 

 taceae. Ophiostoma ulmi (Buis.) Nannf. Perithecium with emerging mucilaginous 

 mass of ascospores. (A-B, after Greathouse and Ames: Mycologia, 37(1):138-155. 

 C-D, after Ellis and Everhart: The North American Pyrenomycetes. E-F, after 

 Berlese: Riv. patol. vegetale, 1(1):5-17; (2):33-46. G, after Buisman: Tijdschrift over 

 Plantenziekten, 38(1) :l-5.) 



