36 



Mycologia 



closely the take-all organism. Since several authors have men- 

 tioned O. herpotrichus in connection with the disease, it, however, 

 must be considered. The perithecia as pictured by Berlese resem- 

 ble somewhat those of O. cariceti, but the asci and spores are very 

 different. The spores are twice as long as those of the take-all 

 organism, and are flexuous, thread-like, multiseptate, and brown. 

 Confusion of the two species, therefore, is impossible. 



Since the published diagnoses of 0. cariceti are very brief and 

 incomplete, the following description has been prepared. It is 

 based on the specimens oi S. cariceti received from Kew and on 

 several collections of American and foreign material of the fungus 

 found associated with the take-all disease. Consideration of the 

 appearance of the fungus in pure culture is omitted. 



Ophiobolus cariceti (Berk. & Br.) Sacc, Sylloge Fungorum 2: 

 349. 1883. 



Sphaeria cariceti Berk. & Br., Ann. & Mag. Nat. Hist. 7: ser. 3. 

 •455. pi 17. fig. 35. 1861. 



? Rhaphidophora graminis Sacc, Nuovo. Giorn. Bot. Ital. 7: 307. 



1875- 



? Ophiobolus graminis Sacc, Revue Mycol. 3: No. 11. 45, 1881 ; 

 and Syll. Fung. 2 : 349. 1883. 



Mycelium permeating the roots of the host, causing them to 

 become very brittle and easily broken away, developed profusely 

 above the crown of the plant in and about the leaf sheaths, and 

 forming a definite thick plate between the inner leaf sheath and 

 the culm; the mycelial plate (Fig. 5) usually adhering to the culm 

 when the leaf sheaths are stripped away, composed of coarse, dark 

 brown hyphae, three to six microns in diameter, which frequently 

 run rather definitely parallel to one another forming broad, flat, 

 ribbon-like strands resembling somewhat compressed rhizomorphs ; 

 perithecia membranaceo-carbonaceous, dark brown to black, 

 smooth, rostrate, ostiolate, occurring on the roots of the host espe- 

 cially within thick wefts of fine rootlets developed abnormally 

 about the crown of the plant, but more frequently observed arising 

 from the mycelium beneath the outer leaf sheath, standing singly or 

 in groups, the individuals in a group occasionally fused laterally but 

 no true stromatic tissue developed, firmly bound to the leaf sheaths 

 by numerous strands of mycelium attached both to the neck and 



