7i6 FUNGt 



They are resting-spores which usually lie dormant during 

 winter and germinate in spring; they can, however, germinate 

 after being kept for several years, and are capable of with- 

 standing considerable variations of temperature without injury. 

 The short hypha arising from the chlamydospore is frequently 

 termed a promycelium : Brefeld and others regard it as a 

 basidium-like conidiophore and term it a hemibasidium ; it 

 differs from the typical basidium of the Eubasidii in that it 

 produces a variable and irregular number of conidia instead of 

 a small definite number. 



Although in some species the promycelium penetrates and in- 

 fects the host-plant directly, in the majority of cases it produces 

 conidia (sometimes termed sforidia) whose germ-tubes enter 

 the tissues of young plants. 



The Hemibasidii are divided into two orders or families, 

 namely : — 



(i) The Ustilaginacece. 

 (2) The TilUtiacea. 

 In the former family the conidiophore is divided transversely 

 into 3 or 4 cells (Fig. 240), and its conidia are borne laterally, 

 while in the Tilletiaceae the conidiophore is undivided and bears 

 conidia in a whorl at its apex (Fig. 244). 

 (i) Ustilaginacea. 



3. As examples of the Ustilaginaceae, the 'smut '-fungi so 

 common on the cereals may be studied, 

 (i) 'Smut' of Oats. 



Symptoms. — In looking over an unripe field of oats in June 

 or July ears are seen in which the grains are replaced by a loose 

 brownish or dark olive-coloured powder resembling soot The 

 powder is easily blown or washed away, and after this has 

 happened nothing remains of the ear but the rachis and its 

 branches, the chaffy glumes and the grain being totally destroyed. 



The disease attacks the ears only, and previous to their escape 

 from the uppermost leaf-sheath, the whole plant appears to be 



