34 MASSACHUSETTS HORTICULTUEAL SOCIETY. 



other mycelial threads, at the base of the stalks bearing these con- 

 idial spores, the true sexual spores are produced in something like 

 the following manner : Certain filaments 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 poUenization of the ovule in flowering 

 plants, though differing in method and results. After this fertiliza- 

 tion, sacs or cells arise from the coil, in which spores are formed, 

 and the whole coil and sacs of spores become surrounded by a cover- 

 ing 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 liv- 

 ing tissues, and on these only, including, therefore, the most destruc- 

 tive members of the group. 



Puccinia Graminis, one of the most widely distributed and gen- 

 erally known, is one of the many species of that destructive agency 

 which is often vaguely spoken of as Eust. All agriculturists who 

 have made the raising of grain their leading employment, 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 3'ellow, premature old age. 



The different stages in the growth of this plant are quite distinct 

 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 ma- 

 ture 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 few daj^s a short 

 stem, bearing a crop of other spores of very much smaller size. To 

 avoid confusion we will call these by their scientific name — sporidia, 

 while the parent spores are styled teleutospores. The sporidia have 

 never been known to grow upon the grass or grain ; but when they 

 find their way to the leaves of a barberry bush they soon begin to 



