2^6 Journal of Agricultural Research voi.xv.no.h 



DESCRIPTION OF THE FUNGUS 



From a study of the fungi reported on the rose no description has been 

 found that seems to apply to this organispi. The characters of the 

 ascogenous stage, both in its development in nature and in culture, place 

 it most nearly in the genus Diaporthe. It differs from that genus in 

 having continuous ascospores which may, however, become pseudo- 

 septate. The spores of the genus Diaporthe are typically 2-celled, but in 

 some species they are described as nucleate, i -celled while young, or 

 obscurely septate. The imperfect stage appears to be most closely 

 related to the genus Phomopsis. In view of the above considerations, 

 it has seemed that for the present the fungus may best be referred to the 

 genus Diaporthe and will be described as Diaporthe umhrina. 



Diaporthe lunbrina, n. sp.' 



Pycnidia subglobose to lens-shaped, walls generally rather thin, thickened at apex, 

 embedded, rupturing the epidermis, irregularly ostiolate, simple or chambered, 200 

 to 300 IX in diameter; pycnospores subfusoid, straight or slightly curved, hyalin, 

 4.8 to II. 2 by 2 to 3.2 ix; sporophores simple or branched, tapering above, 12 to 40 m 

 in length. 



Perithecia membranaceous, two to five, immersed in a valsoid stroma around 

 pycnidium, globose, with beak scarcely projecting above the epidermis, 100 to 290 n 

 in diameter; beaks 150 to 195 n in length; asci clavate, subsessile, aparaphysate, 30 

 to 50 by 6.4 to 8 /x; spores elliptical, usually hyalin, when mature sometimes light 

 olivaceous, continuous or sometimes with one pseudo-septum, 8 to 11. 2 by 3.2 to 4 ix. 



Forms cankers on the stems of cultivated roses. 



Type material collected at Arlington Experimental Farm, Virginia, April, 1917. 

 Specimens deposited in the herbarium of the Office of Pathological Collections, 

 Bureau of Plant Industry, United States Department of Agriculture, Washington, 

 D. C. 



In figure i is shown a pycnidium as it occurs in nature. The basal 

 wall of the pycnidium is often very much thickened near the center, 

 projecting upward in the cavity of the pycnidium. Protrusions may 

 develop from other portions of the wall, forming a chambered pycnidium 

 as illustrated in figure i , a. The parenchymatous upper portion of the 

 pycnidium is composed of small, closely packed, thin-walled cells. The 

 fungus suggests somewhat the appearance of a species of Myxosporium 

 in certain sections through the pycnidium in which the thickened upper 

 portion has apparently fallen away. Great variability was apparent 

 in the development of the pycnidial stage in culture. It was observed 

 that on prune-agar poured plates made from stage A that the spores 

 were first borne directly from the mycelium and that an abundance of 



1 Diaporthe umbrina, sp. nov.— Pycnidiis subglobosis vel lenticularibus, parietibus plerumque aliquid 

 tenuibus, apice incrassatis, Lmmersis, epidermidem mmpentibus, irregulariter ostiolatis, simplicibus vel 

 locellatis, 200-300 m diameter pycnosporis subfusoideis, rectis vel curvulis, hyalinis, 4.8-11.2X2-3.2 ti, 

 sporophoris simplicibus vel ramosis, attenuatis, 12-40 n longis; peritheciis membranaceis, 2-5, valsea 

 stromate circa pycnidium immersis, globosis, rostratis, 100-290 m diameter; rostris saepe supra epidermidem 

 prominentibus, 150-195 ^ longis; ascis clavatis, subsessilibus, aparaphysatis, 30-50X6.4-8 m; sporis ellip- 

 ticis, plerumque hyalinis, maturis interdimi pallide oUvaceis, continuis vel interdum i-pseudo-septatis, 



8-11.2X3.2-4M- 

 Cancros in sannentis Rosanmi cultarum fonnans, Arlington, Virginia. 



