248 



HORTICULTURE FOR SCHOOLS 



SPORES 



extracting nourishment and rendering them useless. As this 

 process goes on, the fungus gradually gains in size and 

 strength, and spreads rapidly in all directions to the un- 

 affected portions of the plant tissue. After a certain stage is 

 reached, the fungus puts forth a new type of growth which, 

 in most cases, extends outward through the epidermal cells 

 of the plant into the air. On the ends of this new growth, 

 sacs form containing spores. These are soon scattered to 

 other leaves or plants and the process begins 

 all over again. Since in many cases the spore- 

 sacs produce hundreds and even thousands of 

 spores, and since each fungus bears many such 

 sacs, it is easy to understand that the disease 

 will spread very rapidly unless checked. 



359. Control. It is clear that the fungus 

 must be controlled before it gains access to the 

 tissues of the plant. This is accomplished in a 

 number of different ways. If the spores are car- 

 ried to the fields by the seed, the natural method 

 is that of seed disinfection. The material com- 

 monly used for the purpose is a solution of 



FIG. 126. A fun- - . - . , ,. ~ 



gus showing formalin or of corrosive sublimate. Spores gain 



access commonly through wounds in the plant. 

 It is obvious that every care must be taken to avoid injury 

 and thus reduce the possibility of infection to a minimum. 

 Very frequently decay is caused in fruit by careless handling, 

 which bruises the skin and provides means of access for the 

 spores. In view of these facts, the method of fruit handling 

 becomes of the utmost commercial importance. 



The fungicide most commonly employed is some form of 

 sulfur. This may be put on the plant either in the dry 

 state or it may be applied in the form of a spray, the most 

 common materials used being lime sulfur and bordeaux 

 mixture. 



360. Bacteria are very minute organisms exceedingly 



