THE PATHOGEN 



Little information has been published on Rhabdocline pseudot- 

 sugae in the United States and Canada since Weir's original descrip- 

 tion (66). The taxonomy of the perfect stage was completed with 

 Sydow's (58) establishment of the genus Rhabdocline based on the 

 single species R. pseudotsugae. The fungus was placed by Sydow in 

 the family Phacidiaceae of the order Phacidiales. A description of 

 the genus Rhabdocline is as follows: 



Fructifications elongated, subepidermal, without stroma, 

 breaking through the longitudinally splitting epidermis, with 

 convex, brown fruit disk and hyaline small-celled lower layer. 

 Asci clavate, 8-spored. Spores long-ellipsoid, one-celled, hyaline, 

 embedded between simple or branched, coalesced paraphyses. 



Rhabdocline pseudotsugae is described as: 



Fructifications on the under side of the needles, scattered 

 or in longitudinal rows; more or less aggregated and running 

 together at the ends. Reddish-brown flecks more or less visible 

 on the upper needle surfaces. Fructifications of different 

 lengths, up to 3 mm. long, about 300pi wide, and 200jjl high; 

 appearing subepidermal, the epidermis at first rather strongly 

 distending in the form of pustules but the red-brown hymen- 

 ium soon breaking out through a long but not prominent slit 

 on the side or top of the epidermal cover, hence resembling an 

 hysterothecium. This hysterothecium having a basal layer 

 50-70[ji or occasionally up to 200[x thick, made up of hyaline, 

 coalesced hyphae of- 1.5-2pi diameter and underlaid by a loose 

 hyaline plectenchyma tissue of richly ramifying septate hyphae. 

 Underlying hyphae dissolving away while the remainder grow 

 closer with the epidermal inner wall in a more or less distinct 

 thread-cell hymenium continuing to the upper surface of the 

 fructification. No fungal tissue develops above the hymenium. 

 Asci standing parallel, clublike or nearly oblong clublike, 

 18-20[jl x 120-130(x, broadly rounded above, but gradually 

 attenuated below, 8-spored, sitting embedded among coalesced, 

 thready, forked or simple paraphyses. Ascospores one to two- 

 rowed, cylindrical or oblong-cylindrical, broadly rounded at 

 both ends and often somewhat constricted in the middle, 6-9[jl 



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