SECT. in. ." MILDEWS. 295 



zierii. Sphseria bombarda is like an assemblage of minute 

 black beads lying flat and crowded together upon de- 

 cayed wood ; each bead is an oblong vesicle pierced at 

 the apex for the emission of the microscopic sporidia, 

 or spore cells. The Sphseria aquila, found upon decayed 

 wood, has its fruit-bearing vessels seated upon thickly 

 matted fine threads. In some species they are in tufts ; 

 others have bottle-shaped perithecia sunk into the 

 stems of the berberry, laburnum, and decayed oak 

 palings ; and lastly the candle snuff Sphseria may fre- 

 quently be seen like patches of soot at the bottom of 

 stakes or gate posts. More than two hundred well as- 

 certained species of the genus Sphseria are native in 

 Great Britain alone. 



The genus Nectria, which forms a connecting link 

 between the genera Peziza and Sphseria, has several 

 interesting species, as the Nectria Peziza, which grows 

 in a congeries of most minute cups forming a bright 

 orange-coloured patch on decayed stumps of trees. 



In the order Perisporacei the perithecia, or external 

 cases, are free and become dehiscent at last, but when 

 young these fungi consist of cellular jointed filaments 

 like necklaces, rising upright from their mycelia, and 

 bearing reproductive bodies. In this state they con- 

 stitute the mildew on the vine, rose tree, turnip, hop, 

 pea, &c. They are true parasites, appropriating the 

 juices, and filling up the breathing pores of the leaves, 

 so as to cause disease and often death. The vine 

 mildew, which has been called Oidium Tuckeri, but 

 which is now supposed to be an imperfect state of 

 Erysiphe, never advances beyond this state, consequently 

 it never has more than one form of fruit. Mr. Berkeley 

 has discovered that, on the contrary, the hop and pea 

 mildews, which belong to the genus Erysiphe, have five 

 different modes of reproduction. The destructive power 

 of these fungi is strongly illustrated by the extraordinary 



