CLASSIFICATION OF FUNGI 61 



vanillae, Del., which attacks the vanilla; and an un- 

 determined species on Hevea braziliensis. 



In the genus Ascochyta the pycnidia are embedded in 

 very much discoloured tissues of the host plant. The 

 conidia are ovoid or oblong, clear, and two-celled. In 

 this genus we find the A. nicotianae, Pass., of the 

 tobacco (see page 153) ; A. pisi, Lib., of the pea (page 

 230) ; A. corticola, and an undetermined species on the 

 citrus fruits. The genus Discosia, which belongs to 

 this order, contains D. theae, Cavara, which attacks the 

 tea ; and the genus Dematophora contains D. necatrix, 

 Berlese, which attacks the tea and many other plants. 



In the genus Aschersonia we find a number of very 

 important and interesting species. They differ widely 

 from the great majority under consideration in that 

 they attack and destroy great numbers of insects which 

 are injurious to our crops. Among the most important 

 are A. aleyrodis and A. flavocitrina, which attack the 

 white fly (Aleyrodes) and many scale insects of Florida 

 and the American tropics, and A. sclerotioides, which 

 attacks the scale insects. 



Basidiomycetes 



The class Basidiomycetes is subdivided into Hemi- 

 basidiomycetes, the Protobasidiomycetes, and Auto- 

 basidiomycetes. 



Under the Hemibasidiomycetes we have the order 

 USTILAGINALES or Smuts, which are very abundant on 

 many plants, especially the cereals, wherever grown. 

 The fungus is first observed in the flower, leaf, or stem 

 as small (or in the case of corn as large) tumours or 

 nodules which are white and spongy. In a very short 

 time these nodules become filled with great masses of 

 black (occasionally light-coloured), greasy spores which 

 are known as chlamydospores. Under suitable con- 

 ditions these spores germinate, producing small pro- 

 mycelia, on which are formed the true spores or 

 sporidia ; these in turn grow, producing a mycelium 

 which penetrates the host plant. 



