116 TRANSACTIONS OF THE 



RUST 



A Lecture before the State Agrieiiltural Society, September 12th, 1879.. 



By Professor C. H. Dwinelle, 



Lecturer on Practical Agriculture in the University of California, Berkeley. 



The following lecture is the result of a request of the State Agricul- 

 tural Society to Professor Dwinelle, of the State University, to give 

 the society his views concerning rust in wheat. September twelfth 

 was the time appointed for the delivery of the lecture, and Pioneer 

 Hall was the place. Below the lecture is given in full : 



To begin with: What is this rust of which we hear so much as an 

 enemy to the wheat crop ? Rust is a fungus ; just as truly a plant 

 as the wheat which it grows upon. There are many large funguses 

 with which we are familiar, as the mushrooms, toadstools, and tho 

 like, but a large part of them can be seen only imperfectly, or not at 

 all, without the aid of a microscope. Funguses have no flowers and 

 no seeds. In place of seeds there are produced what are called spores; 

 that is, simple plant cells which are capable of growth and reproduc- 

 tion of their kind. These spores are produced in great numbers, and, 

 if visible to the naked eye, appear like dust. Under the microscope 

 they are seen to be exceedingly various in form in different species,. 

 and often very beautiful. Funguses are parasites; that is, they live 

 upon other organized matter, either animal or vegetable. Some of 

 them prefer living food, and some flourish upon that which is decom- 

 posing. They have not the green color which we usually think of as 

 belonging to a vegetable. That color is produced by a substance called 

 chlorophyl, which is one of the agents in assimilating the crude 

 material taken up from the earth by plants and fitting it for plant 

 food. As a fungus lives upon organized matter, which has already 

 gone through this process, it has no need of chlorophyl. 



The sickly appearance of rusty grain, and the red powder which 

 rubs off from it, are familiar to every farmer, but few have had the 

 opportunity to follow it through its various stages of development. 

 Even among x^rofessional botanists there has not been the full knowl- 

 edge of this subject that is desirable. By degrees, however, order has 

 been brought out of confusion. What were supposed to be distinct 

 species of fungus have been identified as simply different develop- 

 ments of the same thing. When a wheat plant is attacked by rust, 

 yellow spots appear upon the leaves. The cuticle is raised over these 

 spots, as if by pressure from within, so as to give the appearance of 

 more or less elongated pustules. Finally the* pustules burst by the 

 splitting of the cuticle. Under a good glass the pustule is seen to be 

 full to overflowing with spores in various s'tages of development. 

 They are simple vegetable cells, globular or nearly so, and attached 



