(icrniuiatioii of Spores. 



^3 



a. h. 



Pig. l.—Ustilago avence or Oat Smut.— a. Spore gerniiuating and giving 

 off conidia from germinal tube or promycelium x 450. b. Colony of sprouting 

 conidia, developed from one of the conidia in a x 350. (After Brefeld.) 



2. In Ustilago hromivora the conidia produced by the germinal tube are 

 not sprouting conidia, but they form n-w germinal tubes or promycelia, which 

 in turn produce similar conidia. (Fig. 2.) As a rule the, promycelium is only 

 formed once direct from the spore, but here it is repeated, and is not confined 

 to the germinating spore. 





Fig. 2. Ustilago hromivora or Brome Smut. — -A single spore producing a 

 two-celled promycelium, which forms conidia, and these conidia in turn again 

 develop a promycelium, and so on until quite a number is formed, as in Figure 

 X 400. (After Brefeld.) 



3. In Ustilago olivacea the germinal tube is in abeyance, and conidia are 

 formed direct from the spore. These conidia multiply indefinitely in a 

 nutritive solution by sprouting in a yeast-like manner. (Fig. 3.) 



^8 f. 



)#= 



Fig. 3. Ustilago olivacea or Carex Smut. — Spores producing conidia direct 

 without the intervention of a germinal tube x 400. (After Brefeld.) 



