584 STATE BOARD OF AGRICULTURE. 



or through cells or which would cause a falling apart of the cells of celery 

 tissue through dissolution of the middle lamella, if produced by the fungus, 

 are at least not present in sufficient quantities to show noticeable results in 

 exjoeriments of this kind. Sections of diseased plants show the hyphae 

 ramif3dng through all parts of the tissue, forming a perfect network of threads 

 through the cell walls and protoplasm. Apparently hyphae are capable of 

 penetrating cell walls at any point at which they come in contact and of 

 running through cell walls, protoplasm or intercellular spaces as these are 

 encountered. Hyphae have been found in all the various tissues of the cel- 

 ery plant. In the later stages of disease, mycelium sometimes even produces 

 extensive growth in the vascular system. Neither stained nor unstained 

 sections reveal injury preceding invasion as is noted with many rot produc- 

 ing organisms. Even after penetration the cell is not immediately destroyed; 

 many invaded cells, but for the presence of mycelium, could not be dis- 

 tinguished from cells of normal unattacked tissue. The first indication of 

 .change in the invaded cells comes about through a disintegration of pro- 

 toplasm, followed by production of browm coloring matter in the cell walls 

 preceding a general break down and collapse of diseased tissue. Many soil 

 organisms no doubt come in at this point and continue the work of destruc- 

 tion. It is to these latter organisms that we attribute the true rotting found 

 in diseased plants as the primal organism concerned, while effective in kill- 

 ing tissue, is incapable of producing a typical rot such as is usually encounter- 

 ed in diseased specimens which are found in the field. 



Physiological Relations. 



CULTURAL CHARACTERISTICS. 



The fungus grows readily on all of the common laboratory media and on 

 many other media which have been prepared and used in cultural studies. 

 It is easily isolated by the dilution method when pycnidia are present. Single 

 spore colonies appear as thin feathery growths, so characteristic of many 

 of the Fungi Imperfecta The colonies are at first white; after four to eight 

 days, on certain media, the superficial growth is bluish or bluish-green. 

 The submerged threads are hyaline to black. Acidity, high temperature, 

 and carbohydrates seem to favor color production in the mycelium. Pro- 

 teins, low temperature, and alkalinity tend to cause little color production. 

 A protein medium also tends to cause perm.anent loss of potentialities for 

 color production, and for pycnidium production, as well as loss of virulence. 

 Pycnidium production is sparse on all media solidified with agar and on sterile 

 vegetables, with the exception of celery plugs. Ten to twenty days are 

 required for pycnidia to develop. Characteristics of growth on different 

 media are given briefly in a tabular form in the following outline. 



