Fitz Patrick, Thomas, Kirby : Ophiobolus 37 



ascigerous portion, often developed in great numbers, more than 

 one hundred individuals having been counted on a single culm, 

 when young hidden from view but at maturity the beaks protruding 

 and prominent, and by the shredding of the leaf sheath the upper 

 hemisphere of the perithecium often exposed to view; perithecial 

 beak developed obliquely and in the beginning lying more or less 

 parallel to the surface of the culm, later, curving sharply outward, 

 penetrating the leaf sheath and protruding, the obliquely attached 

 curved beak so characteristic of the species as to be almost diag- 

 nostic (Fig. i) ; ascigerous portion of the perithecium globose or 

 subglobose, though sometimes compressed between the leaf sheaths, 

 330—500 fx (usually about 425 /a) in diameter, narrowing gradually 

 into the truncate-conoid to cylindrical beak which frequently at- 

 tains a length as great as the diameter of the ascigerous cavity 

 (Fig. 2) ; asci (Fig. 4 and Text Fig. ib) numerous, fascicled, 

 elongate-clavate, straight or curved, short stipitate to subsessile, 

 90-115 x 10-13 /i,, rounded at the apex, 8-spored, thin-walled; 

 paraphyses (Fig. 3) abundant, thread-like, flexuous, unbranched, 

 hyaline; ascospores fascicled to sub-biseriate, hyaline, as viewed 

 together in the ascus faintly yellowish, linear, curved, broader at 

 the middle and tapering gradually toward the ends, the upper end 

 rounded, the basal end more acute and sometimes more sharply 

 curved, 60-90 (chiefly 70-80) x 3 fi, when young continuous and 

 multiguttulate, at maturity 5-7-septate, not reaching morphological 

 maturity until late autumn or winter. 



Parasitic on wheat, barley, rye, and various wild grasses, causing 

 the take-all disease, apparently cosmopolitan in its distribution. 



Department of Plant Pathology, 

 Cornell University, 

 Ithaca, N. Y. 



Explanation of Plate io 

 Ophiobolus cariceti 



All the figures were made from American material collected on wheat plants 

 showing the typical symptoms of the take-all disease. 



Fig. 1. Two perithecia developed below the outer leaf sheath. The oblique 

 beaks illustrate one of the most characteristic features of the species. X 35. 



Fig. 2. Three perithecia illustrating variation in shape. They are shown 

 as they appear in a microscopic mount after removal from the plant, and no 

 attempt was made to orient them in the erect position. X 35. 



Fig. 3. A fascicle of asci and paraphyses. X 240. 



Fig. 4. Asci. X 300. 



Fig. 5. A portion of the mycelial plate formed about the culm. X 300. 



