204 e. MacKinnon. 



promycelium comes in contact with another spore it may 

 form a nodular growth round it (O. 7), and there appears 

 to be a fusion of the protoplasm. The growing mycelium 

 stains readily with carbol-fuchsin, and (C. 6) shows the 

 central mass of protoplasm in the spore extending into the 

 hyaline projection, and as a central core with a clear 

 enveloping sheath in the longer promycelium. 



Explanation of Plates. 



Plate X. — Cross section of floret of Panicum flavidum, showing 

 central core of tissue, spore balls of Sorosporium panici and 

 glumes G. 1, G. 2, G. 3. 



Plate XI. — Cross section of spikelet of Panicum gracile (dis- 

 torted head) showing core of tissue with cavities filled with 

 spores of Ustilago panici-gracilis, and thin enveloping mem- 

 brane. 



Plate XII. — Photograph of Panicum gracile affected with 

 Ustilago panici-gracilis, showing normal inflorescence and 

 distorted inflorescences. 



Plate XIII. — Germination of Spores. B (1 — 7) Sorosporium 

 panici in nutrient solution (Duggar); (8 — 10) in Knop's 

 solution. C (1 - 7) Ustilago panici-gracilis. 



