Dec. 16, 1918 



Brown Canker of Roses 



597 



Fig. I. — Diaporilie u?nbrina: a. Vertical section of 

 a pycnidium in nature, X 80; b, simple and 

 branched sporophores; c, pycnospores, X 360. 



thin- walled membranous pycnidia soon developed. The fungus was 



transferred to the rose-stem medium, where the pycnidial development 



was similar to that in nature, the 



pycnidia being simple or somewhat 



chambered, 140 to 375 lu. in diameter 



with the walls in the upper portion 



somev/hat more stromatic. The 



perithecia develop in the stromatic 



growth below the pycnidia which in. 



culture become erumpent. Plate 



46, C, shows an enlarged portion of 



a culture, with protruding beaks of the perithecia. In culture there may 



be as many as eight perithecia in a stroma, measuring 290 to 400 



H, with beaks 250 to 500 ^u in 

 length. Figure 2, a, shows a 

 vertical section of perithecia in 

 nature. It will be observed 

 from this illustration that in 

 nature the beaks of the perithe- 

 cia which extend toward the 

 pycnidial rupture in the epider- 

 mis do not protrude propor- 

 tionally as far as they do in 

 culture. In figure 3 is shown 



the arrangement of the perithecia and pycnidia as they occur in nature. 

 The development of pycnospores on the host and in culture is similar. 



The filiform spores which sometimes 



develop in species of Phomopsis in 



addition to the typical fusoid spores 



have not been observed. The pyc- 

 nospores germinate readily, producing 



one or two germ tubes. The sporo- 

 phores, which are sometimes branched, 



are variable in length, but generally 



measure from 12 to 20 ji. The base of 



the sporophore is often broad and ir- 

 regular in shape, becoming very slender 



above (fig. i, b). The ascospores in 



nature are most often continuous, but 



they may be 2-guttulate or i-pseu- 



doseptate. Upon germination the spores 



become 2-guttulate or pseudoseptate and may be slightly constricted 



at the center, and one germ tube is produced toward each end of the 



spore (fig. 2, b, c, d). 



Fig. 2. — Diaportheumbrina: a. Vertical section of perithecia 

 in nature, X 80; h, an ascus; c, ascospores; d, germinating 

 ascospores, X 420. 



Fig. 3. — Diaporthe umbrina: Tangential sec- 

 tion showing relative arrangement of pycni- 

 dium and perithecia in nature, a pycni- 

 dium surrounded by five perithecia; a, pro- 

 liferous stratum extending upward from 

 base of pycnidium. 



