MISCELLANEOUS PAPERS. 259 



spores require the actual presence of water in the shape of drops for 

 their germination ; moisture alone is not sufficient. After having been 

 in contact with water for some time, the cell-walls of these spores are 

 ruptured and a number of still smaller spores escape from them ; these 

 are called goospores, and are possessed with locomotive power; they 

 move around upon the water very rapidly for some time by means of 

 two hair like projections called cilia. After a short time they stop 

 moving around, when they commence to germinate by sending out a 

 germ-tube to start the fungus at a new place. Prof. N. B. Pierce says 

 that the presence of a very small amount of copper salts is fatal to 

 them, hence the value of spraying with copper compounds. The tem- 

 perature most favorable is 30° O.=30° F. Aside from this spore form, 

 there is another, oospores ; these are the results of a special sexual 

 process, fully described by leading botanists. Prof. Galloway tells me 

 in a recent letter that an oospore is a product resulting from fertiliza- 

 tion of an ovum by a sperm cell. 



Powdery Mildews (Erysipheal). — This is a group of fungi doing 

 a great deal of harm to fruit-growers. Grapes, gooseberries, cherries, 

 etc., suffer from members of this group. The spores of all of these 

 are producrd in about the same manner, so that one description will 

 answer for all, as space would not permit me to go into details. Unlike 

 in the case of the downy mildew, the actual presence of water is not 

 required for the germination of the spores of the powdery mildew; in 

 fact, they prefer a rather dry season. The difference is so great that 

 one will flourish where the other one would perish. Another great 

 difference is that the whole plant-body of the powdery mildew, together 

 with their spores, are fully exposed on top of the leaves or fruit, as the 

 case may be ; they get their nourishment by means of little suckers 

 which penetrate the epidermal cells. 



This sulphur treatment usually gives good results, as in the case 

 of the powdery mildew of the grape ( Uncimila spiralisj. I may remark 

 that this fungus is in some sections better known by the name Oidium 

 Tuckeri. This name, however, means the conidia form of this or a 

 similar parasite of the vine, which exists in France, where they claim 

 that it was brought there from the United States. If so, it was un- 

 doubtedly in exchange for a good supply of other parasites. 



The powdery mildews are usually first noticed upon the upper 

 surface of the young leaves and on the buds as they begin to leave out. 

 They are usually reproduced by means of summer or non-sexual spores 

 called conidia. They are, as stated before, capable of germinating in a 

 very short time, which is done by sending out a germ-tube to start the 

 fungus at a new place. There is another spore form known as asco- 



