290 Wisconsin Statb Horticultueal Socibtt. 



asexual spores. On other mycelial threads, at the base of the 

 stalks bearing these conidial spores, the true sexual spores are 

 produced in something like the following manner : Certain fila- 

 ments first begin to coil up into a close spiral, after which another 

 thread grows up and touches the tip of this coiled filament and 

 fertilization takes place, a process essentially the same as the 

 pollenization of the ovule in flowering plants, though differing in 

 method and results. After this fertilization, sacs or cells arise 

 from the coil, in which spores are formed, and the whole coil and 

 sacs of spores become surrounded by a covering of cells. On 

 account of the sexual spores being borne in these sacs or asci^ this 

 fungus comes among the Ascomycetes, one of the highest groups 

 of fungi. 



We come now to speak of species of fungi which flourish on 

 living tissues, and on these only, including, therefore, the most 

 destructive members of the group. 



Puccinia Graminis, one of the most widely distributed and 

 generally known, is one of the many species of that destructive 

 agency which is often vaguely spoken of as rust. All agricult- 

 urists who have made the raising of grain their leading employ- 

 ment, will at once turn in thought to the time when their whole 

 field of growing wheat or oats, the pride of their vocation, was 

 turned, as by the stroke of some unseen demon, into a yellow, 

 premature old age. 



The different stages in the growth of this plant are quite dis- 

 tinct and peculiar, and though somewhat complicated, it would 

 not be justice to the plant or to science to omit the history of the 

 forms through which the rust plant passes from the perfect state 

 to the perfect state again. 



The transformations in the life of a butterfly are so evident 

 that the merest schoolboy may observe the truth for himself ; but 

 with the rust plants the objects are so very small that the changes 

 can only be seen by the keen eyes of a skilled observer, with the 

 best powers of the microscope. Beginning with the spores of the 

 mature rust plant, as seen in the black stains on the old stubble 

 of any grain field, it will be found, when the warm and moist 

 days of spring come, that these spores germinate, producing in a 



