now FUNGI LIVE IN WINTER. 



617 



rapid propagation of its kind during the growing season, and finally 

 stores up its vitality in dark, thick-coated spores that remain on the 

 stubble through the winter, and are not injured by sudden and severe 

 changes in the weather. 



It is due the reader, in passing, to state that one or more of the four 

 forms of spores here briefly mentioned may be omitted. In warm 

 climates it is possible for the winter spores to be dispensed with, the 

 ordinary rust-spores being able to remain alive and continue the life 

 of the pest. It is also believed that in regions unknown to the bar- 

 berry the cluster-cup form may also be omitted. Like all other living 

 things, the rusts accommodate themselves to circumstances, though 

 watchful that their members do not decrease from any lack of vigi- 

 lance on the part of these parasites. 



The order Perisporiacece illustrates our subject still further. The 

 members of this group of fungi are mainly parasites upon higher 

 plants, forming a whitish, web-like film over the surface of the affected 

 parts. In the early life of these white mildews, the horizontal threads 

 send up vertical filaments in which partitions rapidly form at regular 

 intervals. The cells thus produced are spores which fall away in suc- 

 cession from the top. A single vertical filament is shown at I, Fig. 9. 



Fig. 9.~Spork Fobmation of White Mix-dews. 



The spores thus produced are minute, the winds easily disperse them, 

 and they quickly germinate, giving rise to new filaments of mildew. 

 The formation of the sexual or wdnter spores begins late in the season 

 and is shown in the remaining portions of the engraving. When these 

 spores are to be formed, two filaments, crossing each other as shown at 

 III, send out short projections. One of these, c, becomes the female 

 part, and the other, h, the male portion. As a result of fertilization, 

 eight or more branches, IV, h, grow up from the base and envelop the 

 female cell. These branches continue to grow until a thick, hard cov- 



