142 Illinois State Laboratory of Natural History. 



It needs no argument to show the practical value of the 

 studies undertaken upon these minute — probably degraded — 

 members of the vegetable world, for they subsist on living 

 plants of the higher orders, upon which our domestic animals 

 and ourselves depend for the means and materials of physical 

 existence. It is not, indeed, usually known or suspected what 

 proportion of our crops and useful vegetation is destroyed by 

 the microscopic growths which live as parasites or saprophytes 

 upon them; but when we come to understand that in very 

 great measure the things called "blights," ''mildews," ''rusts," 

 "smuts," "rots," "ferments," etc., are really due to the despoli- 

 ations of these same microscopic but multitudinous forms of 

 fungi, some appreciation can be gained by anyone, even with a 

 moment's thought, of the immense aggregate loss that occurs. 

 Perhaps, in one sense, it is well that cultivators do not fully 

 realize the number and variety of parasitic growths which 

 await the development of their valuable plants, and which are 

 liable so badly to injure the latter, and so seriously to affect the 

 receipts for the expended labor. Surely in many cases there 

 would be sufficient ground for discouragement and hesitation 

 to venture in opposition to such an array of dangerous enemies, 

 against whose insiduous and covert attacks fighting seems futile. 



But knowledge of the existence of such things cannot 

 make that existence more hazardous, nor the results more dis- 

 tressing; while here, as in the other battles of life, to be fore- 

 warned is to be forearmed. Knowledge is power, and as much 

 so in this case as in any other; if the latter is still wanting, it 

 is only because the former has not been attained. Is it attain- 

 able? There are difficulties in the way. The objects are very 

 minute; we cannot see them by the unaided eye as individuals, 

 we cannot thus watch their modes of dissemination, germina- 

 tion, growth and development, we only see them, if at all, in 

 the mass, and know of their presence by their results. They 

 have singular, and to the students of other forms of life, unfa- 

 miliar physiological powers and properties; they assume pecu- 

 liar disguises, and pass through unlooked-for stages of develop- 

 ment, of which the connecting links are hard to make out; 

 they lie dormant now, and again become wondrously quickened 

 and enormously multiplied under circumstances not readily 



