TWO NEW GRASS SMUTS. 203 



On Panicum gracile, R.Br., Nyngan Experiment Farm, 

 E. MacKinnon, February 1911. 



Morphology: — The inflorescence when badly attacked is 

 completely altered (Plate XII), forming a contracted and 

 irregularly swollen boil-like growth. Serial sections show 

 a central mass of plant tissue with numerous vascular 

 bundles. Cavities filled with spores (Plate XI) occur in 

 this core, and the whole is surrounded by a thin enveloping 

 membrane which appears to originate from the leaf sheatli, 

 and which ruptures irregularly to allow the escape of the 

 black powdery spores. No trace of definite spore balls is 

 evident throughout the whole series of sections. That this 

 is a different smut to Sorosporium panici is shown by the 

 absence of spore balls by the slightly darker and more 

 distinctly echinulate spores, the variations in germination 

 and its marked difference on the inflorescence. 



Germination: — Spores placed in water commenced to 

 germinate in forty-eight hours sending forth a hyaline pro- 

 mycelium (Plate XIII, C. 1) or in many cases two pro- 

 mycelia (0. 5), one usually larger than the other and 

 developed from opposite sides of the spores, or the pro- 

 mycelium may divide at the base. For the development 

 of conidia a nutritive solution 1 gave the best results; Knop's 

 solution was not so satisfactory, and no conidia were formed 

 in water. The promycelium may be quite long or relatively 

 short when septa first form (O. 2 and 3). The septa may 

 appear near the spore or near the distal end. Branches 

 soon form, often at right angles (C. 4). Conidia are pro- 

 duced laterally or terminally — very frequently by a con- 

 densation of the protoplasm into masses which leave the 

 promycelium as a hyaline empty sheath. Where two pro- 

 mycelia come into contact a fusion may take place, often 

 producing a knotty, irregular mass, and similarly when a 



1 Duggar, Fungus Diseases, p. 26. 



