Oct. 7-Dec. 30, 1918 



Illustrations ix 



Page 

 Plate 43. A.— Cross section of petiole of mature plant showing severe necrosis. 

 B.— Cross section of nodal region of stem tip showing formation of large 

 lysigenous cavities extending from cortex to pith and involving inner 



phloem groups and metasylem 57° 



Plate 44. A.— Cross section of stem of mature plant, showing necrosis of in- 

 ternal phloem together with radial elongation of the cells of the perimed- 



uUary zone. B.— Enlarged view of a necrotic internal phloem group 570 



Plate 45. A.— Cross section of midrib of mature plants (Magnum Bonum), 

 showing abnormal development of the vascular tissue with thickenings of 

 the walls of the phloem adjacent to the fibers. B.— Cross section of petiole 

 of mature plant, showing abnormally large development of the vascular 

 tissue of the petiolar wings • 57° 



Brown Canker of Roses, Caused by Diaporthe umbrina 



Plate D. Rose cane showing lesion of the canker caused by Diaporthe umbrina. 600 

 Plate 46. A.— Rose cane showing the appearance of the canker caused by Con- 

 iothyrium fuckelii. B.— A rose stem showing local infections produced by 

 Diaporthe umbrina. C. — Culture of Diaporthe umbrina from stage B on a 

 rose stem showing beaks of perithecia. D.— Culture on a rose stem from 

 stage B showing spore masses extruded from pycnidia. E.— Pycnospore 



masses from culture shown in figure C 600 



Plate 47. Diaporthe umbrina: Results of inoculations A. — Control. B. — 

 Rose stem showing infection produced by inoculation with stage B; cut 

 rose stems placed in moist atmosphere vmder bell jars in the laboratory. 

 C. — Control. D. — Rose stem showing infection produced by inoculation 

 with stage B ; rose plants in the greenhouse 600 



Parasitism, Moi{phology, and Cytology of Cronartium ribicola 



Plate 48. Cronartium ribicola on Pinus strobus: A.— This figure illustrates the 

 etiolated condition of the bark in the case of a comparatively young nodal 

 infection. B.— This figure illustrates an intemodal infection, somewhat 

 older than that shown in figure A, in which the infection apparently orig- 

 inated at the base of the leaf fascicle (o) 660 



Plate 49. Cronartium ribicola: A.— The edge of a pycnium in section. B.— 

 Part of the same section showing the general relation of the elements which 

 go to make up the sorus and their relation to the host cells beneath. C. — 

 Tangential section in the xylem, showing the cut end of a ray and the man- 

 ner in which a haustorium (a) may rise from the hyphse in the ray and enter 

 the lumen of the tracheid ^60 



Plate 50. A. — A figure illustrating the relation of the pycnium (a), the heavy 

 black line at the top, and young secium, to the host tissue. B.— A section 

 through a mature gecium, taken a little to one side of the break in the bark, 

 to show the seciospore chains (a), the multilayered peridium (b), and the 

 overlying host tissue. C— A similar section showing a double pycnial layer 

 (a, Ci), and the location of the cork cambium (b) which cuts out the old pyc- 

 nium ■ ^^ 



Plate 51. Cronartium ribicola: A.— A median section through a young uredi- 

 nium forming in the space beneath a stoma. B. — A section through the 

 same uredinium as that shown in Plate 55, C, taken to one side of the break 

 in the peridium , toward the edge of the sorus. C— An internal uredinium 



from the cortex of Ribes hirtellum 660 



88097°— 20— 2 



