CABPOPHTTA. 189 



contact with the projecting iilament (trichogyne), doubtless 

 by means of winds, the result of which is the rapid upward 

 growth of filaments which ultimately produce spore-sacs 

 and spores in disks, as above described. 



348. The Plum-pocket Fungus, which distorts the young 

 plums in spring and early summer, is a greatly reduced 

 cup-fungus (family Gymnoascacece). Here the parasite 

 consists of delicate threads which penetrate the tissues of 

 the plum, eventually producing on the surface poorly 

 developed spore-sacs which are not aggregated into 

 cups. 



349. Yeast-plants. — The greatest degradation of the 

 cup-fungus type is reached in the minute plants which 

 occur in yeast. If a bit of yeast be placed upon a glass 

 slip and carefully examined under high powers of the 

 microscope, there will be seen very many small roundish 

 or oval cells, of a pale or whitish color. They have a cell- 

 wall, but generally the nucleus is wanting or indistinct. 

 These little cells are Yeast-plants, and bear the name of 

 Saccharomyces cerevisise. 



350. They reproduce by a kind of fission, called budding. 

 Each cell pushes out a little projection which grows larger 

 and larger, and finally a cell-wall forms between the two, 

 which sooner or later separate from one another [a and i, 

 Fig. 112). Under favorable circumstances certain cells 

 form spores internally, as in c. Fig. 112; and these are 

 now regarded as spore-sacs (asci) homologous with the 

 spore-sacs of the higher, cup-fungi. Yeast-plants are, 

 therefore, to be considered as greatly reduced sac-fungi, 

 and they are members of what is probably the lowest family 

 (Saccharomycetacem) of the order Discomyceteae. 



351. Yeast-plants are saprophytes, and live upon the 



