(•,o2 STATE BOARD OF AGRICULTURE. 



MORrilOLOGY OF CAUSAL ORGANISM. 



The Spore : 



The spores of the Septoria stage are filiform and hyaline varying from 

 00-120 microns in length to 24 microns in thickness, divided into from 

 8 to 9 cells. The thickness of a spore is not nniform throughout. The 

 shape of the ends varies from pointed to globose. (Plate 8 Figure 1). 



The Mycelium: 



The mycelium of this fungus is composed of frequently septate, vacuo- 

 late threads. These threads have a diameter of from 2 microns to 3 

 microns. The mycelium may be said to show two types — the hyaline 

 thin-walled type, and the dark, closely-septate, heavy-walled type. The 

 former predominates during the vegetative stages of the growth while 

 the latter precedes the stroma and pycnidium production. The character 

 of these types of mycelium is brought out by figures. (Pis. 7 and 8). 



The Pycnidium: 



A number of tubes of tomato agar, cornmeal agar, and nutrient glu- 

 cose agar were inoculated Avith a pure culture. At the end of every 24 

 hours after the colony was visible to the ualied eye, material from these 

 tubes was killed in Flemming's medium fixing fluid. Material was killed 

 on successive days until exuding spore masses were in evidence. 



The following schedule was followed : 



Flemming's medium 24 hours 



Washed in running tap water 6 hours 



15% Alcohol 15 minutes 



39 % Alcohol 30 minutes 



50% Alcohol 1 hour 



70% Alcohol Over night 



80% Alcohol 2 hours 



95% Alcohol 2 hours 



Absolute Alcohol 2 hours 



i Cedar Oil — § Absolute 1 hour 



\ Cedar Oil — | Absolute 1 hour 



Cedar Oil 1 hour 



Cedar Oil -^paraffin 6 hours 



Paraffin 2 hours 



Transferred to new paraflBn (52°) and embedded after 2 hours. Some sections 5 mm. thick were 

 made. Stains used; Flemming's Triple, Delafield's haematoxylon, Haidenhain's haematoxylon. 



Continuous efforts were made to obtain results with Delafield's haematoxylon and eosin as described 

 by Durand (igil), but with no success. Although the time which the slide was immersed in eosin was 

 varied from 2 seconds to 5 minutes, the carbol turpentine was inadequate to remove the excess stain. 

 Durand's method was then changed in a single particular and excellent differentiation resulted; after 

 immersing the slide in eosin, the excess stain was washed off with absolute alcohol for a second, then was 

 immersed in carbol turpentine and was mounted in balsam. The result was that the mycelium became 

 a deep red and was very easily distinguished from the surrounding tissue. 



As a result of a study of a culture on tomato agar after 62 to 96 hours, 

 the following steps in pycnidium formation were observed : 



The mycelium begins to anastomose and interweave, becoming brown- 

 ed, resembling a closely woven net, so that the fungous tissue seems to 

 be made up of individual cells more or less rounded in shape. This small 

 oval body increases in size while the surrounding mycelium sends out 

 branches which augment this globose body. This enlarging continues 

 24-92 hours. At the end of this time, the pycnidium consists of a hol- 

 low, globose body, without an ostiole, and is 100-375 microns in dia- 

 meter, with a few strands of mvcelium crossing the cavity within. (Plate 

 5, Fig. 1). 



Spore formation takes place in the same manner as described in the 



