152 Botanical Microfechnique 



host must be preserved unchanged; the fungus, with an entirely 

 different chemical and physical make-up, perhaps an alga-like si- 

 phonaceous plant body, also must be preserved intact. Another task 

 may involve cutting a tough piece of wood bearing a delicate Plas- 

 modium, presenting a conflict between the need for drastic methods 

 and refined methods. In order to minimize duplication of procedures 

 in this chapter, it is proposed to use extensive cross references to ap- 

 propriate sections of the text and to give detailed directions for 

 procedures that are not adequately covered elsewhere in the manual. 



SCHIZOMYCETES 



The preparation of slides from cultures of bacteria is described 

 in detail in textbooks of bacteriology. The bacteria are discussed 

 in this manual only in conjunction with a host plant. A few typical 

 examples of plant tissues and their bacterial invaders will illustrate 

 the general methods of processing. Bacterium steioartii invades the 

 vascular system of corn, forming a shiny yellow mass in the xylem 

 elements. Because of the virulence and ease of dissemination of the 

 disease, it is unwise, in regions where the disease is not normally 



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M^ 



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Fk;. 14.1— Vasculai huiullr of Zen, witli haclciial mass (liaclerium steu'arlii) in the 



prolo\^lcIll. 



