Lewis: Black Knot Disease of Dianthera 71 



Explanation of Plates LVIII-LXI 



Plate LVIII, figure i. Portion of aerial stem of the plant showing hyper- 

 trophy opposite the steles and the longitudinal rupture of the host tissue. Both 

 young and older stages are here shown. 



Plate LVIII, figure 2. Older stages than shown in figure i. The fungus 

 areas have become somewhat roughened and tuberculate on the surface. 



Plate LIX, figure i. Transverse section through an affected area. The six 

 peripheral steles and the central one show the effects of the fungus. The 

 ground tissue is normal in portions of the section and shows the changed struc- 

 ture in others. The conidiophore layer may be distinguished around the periphery 

 of the stromata. The clear spaces in the stromata are young perithecia. 



Plate LIX, figure 2. A portion of the conidiophore layer more highly magni- 

 fied. The conidiophores show the concentric zonation which indicates the num- 

 ber of crops of spores they have produced. The dark-colored parenchyma 

 formed by the fungus and host is also shown. 



Plate LX, figure i. One of the peripheral steles showing the formation of 

 additional xylem, the fungal filaments in the vessels, and the changed paren- 

 chyma surrounding the steles. 



Plate LX, figure 2. Portion of the stroma showing the perithecia and broken 

 ragged nature of the surface of the stroma. The perithecia are immersed 

 locules in the stroma. 



Plate LXI, figure i. Portion of the conidiophore layer showing the uniform 

 zonation. X 300. 



Figure 2. Conidiophore and conidiospores. X 800. 



Figure 3. Portion of one of the steles showing the location of the fungal 

 tissue within the vessels. X 380. 



Figure 4. An ascus with the mature spores. X 1,200. 



