202 e. MacKinnon. 



Spore formation :— The spores originate from a central 

 core of plant tissue and the enveloping membrane corres- 

 ponds with the flowering glumes (Plate X). The three 

 outer glumes (G. 1, 2, 3) remain quite unattacked. The 

 spore balls are clearly seen in sections of the floret. 



Germination: — The spores were germinated in nutrient 

 solutions, as practically no germination took place in water. 

 The type of promycelium depends upon the composition of 

 these solutions. In a solution 1 containing sugar, iron 

 chloride, ammonium nitrate, etc., a promycelium is pro- 

 duced which is at first hyaline and generally conical (Plate 

 XIII, B. 1), becoming granular and warty (B. 4), branching 

 either at the apex (B. 3), or at the base (B. 7). Septa 

 appear, few or many and often close together, with the 

 promycelium constricted and conidia are budded off from 

 the various segments, (B. 5 and 6). In Knop's solution 

 (no iron chloride, or sugar, but containing Oa) the pro- 

 mycelium is generally more slender and grows to a greater 

 length before becoming septate (B. 8, 9, 10). Conidia may 

 be produced (B. 9), or the promycelium breaks up into 

 segments (B. 10). In the latter case the promycelium is 

 more granular and stouter than that producing conidia. 



2. Ustilago panici-gracilis, McK. Panicum. 

 Sori involving the whole inflorescence, destroying it, 

 while enclosed in its enveloping leaves, black in the mass 

 and powdery. In some cases the spikelets have expanded, 

 or partly formed before being attacked. Spores dark 

 olivaceous to brownish, varying somewhat in size and 

 shape ; mostly subglobose or oval, sometimes oblong or 

 irregular, not so irregular as Sorosporium panici. Epispore 

 quite distinctly echinulate. Size common, 11/^ diam. or 

 10 x 12/^, varying from 10-15 x 8 — 12ft. A few measured 

 10 X 15, and 10 x 13'6. 



1 Duggar, Fungus Diseases, p. 26. 



