May 6, 1918 



Yellow-Leafblotch of Alfalfa 



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abstricted. When the apothecium is ready to expand, asci appear 

 among the paraphyses, and the ascospores are soon mature and ready 

 to be discharged (fig. 5). 



The apothecia are sessile, 0.25 to i mm. in diameter, rarely larger. 

 The outer wall appears black and is made up of thick-walled cells. The 

 disk of the apothecium appears pale gray when expanded. The stro- 

 matic layer from which the asci arise is continuous with the stroma in 

 the leaf, but it is composed of smaller cells rich in protoplasmic contents. 



Fig. 3. — Pyrenopeziza medicaginis: Conidiophores from a culture at an early stage in the formation of an 



acervulus. 



The paraphyses measure 50 to 80 by 2.5 to 3 /:. Occasionally they 

 branch, in which case a septum may occur. The asci measure 60 to 75 

 by about 10 /x. The ascospores are slightly ovoid in shape and measure 

 8 to 1 1 by 5 to 6 ;u. By far the largest number are 9 to 10 /i long. 



PHYSIOLOGY 



Isolation of the Fungus 



For over a year after the yellow-leafblotch had first been observed, all 

 efforts to isolate the fungus which appeared to be the cause were unsuc- 

 cessful. All attempts to germinate conidia failed. Attempts to plate out 



