SUPPLEMENT 



red spores appear, later brown or black spores show among the others, 

 often quite hiding them. Under the microscope the red spores are 

 seen to be single cells with thin walls, but the dark spores consist of 

 several thick walled cells raised on a stalk. This illustrates a fact 

 that botanists were long in rinding out, the fact that many rusts pro- 

 duce different sorts of spores at different stages. It is also true that 

 the same fungus may, during part of its existence, live on one sort of 

 plant, and later on require quite a different plant for its host. It is 

 certain, for instance, that one kind of rust must spend its first period 

 of life on barberry bushes, and that it produces there spores in cluster 

 cups, that is in little cups imbedded in the leaves. These spores will 

 germinate only when they fall on wheat. The mycelium within the 

 tissue of the wheat produces great quantities of red spores, which, in 

 turn, germinate immediately and produce more red rust, until the 

 whole grain field is infected. As the grain ripens, the same mycelium 

 that produced thin-walled red spores now produces the thick- walled, 

 darker spores that can remain dormant during an unfavorable season. 

 At the beginning of the growing season these spores on the rotting 

 straw germinate, and, like the spores produced by smut on corn, pro- 

 duce great numbers of minute spores ; these spores germinate only 

 when they fall on the barberry, and forming cluster cups, complete the 

 cycle. It is an interesting fact that, long before the life history of 

 wheat rust was known, it was believed that the barberry exercised an 

 evil influence over wheat, and in 1670 the Massachusetts legislature 

 passed laws for the extermination of the barberry. Probably not all 

 rusts pass through as many stages as the wheat rust. In fact it is 

 pretty certain that the rust so common on the malva has neither the 

 cluster-cup nor the red-rust stage. Examples of the cluster-cup stage 

 are more likely to be found in the spring months. In Southern Cali- 

 fornia they are common on Phacelia distans and on nettles. 



The life histories of fungi that affect agricultural products, pro- 

 vided they are known, can often be obtained by applying to govern- 

 ment headquarters. Frequently the stories of discovery in the fields 

 of research are of absorbing interest. The life of Louis Pasteur by 

 his son-in-law is a striking example. 



It should be possible anywhere in California to obtain sufficient 

 material to arouse an interest in lichens. A supply of the larger, 

 more striking kinds from the coast or mountains, once obtained, will 

 last for years ; but the smaller, more common kinds will answer, and 

 children should soon be able to find lichens for themselves on fire 

 wood, rocks, walls or trees in shaded places. Special effort should 

 be made to find specimens with spore-fruits ; these are usually cup or 



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