HYPOCREALES 



245 



The stroma thickens under the outer layer of leaf, and ruptures it length- 

 wise in stripes or welts (Fig. 161, 3). The perithecia are formed in two 

 parallel rows in these cushions. 



In Balansia morphological differentiation of the stroma is more marked 

 since the plectenchyma which surrounds the host becomes more scle- 



Fig. 161. — 1. Oomyces monocarpus. Group of fructifications on bamboo twig. 2. 

 Ophiodotis Henningsiana. Section through an infected leaf. 3. Ophiodotis raphidospora. 

 Section through a rolled leaf showing stroma. 4. Balansia Hypoxylon. Section of pseudo- 

 sclerotium and mature stroma with perithecia. 5. Balansia ambiens. Section of grass 

 stem with perithecial stroma. 6, 7. Balansia redundans. Habit, and section through 

 stem and stroma. 8, 9. Balansia diadema. Section of stroma and infected spikelet of 

 Panicum with fructifications. (1 X 3; 2, 5 X 13; 3, 4 X 4; 6, 9 natural size; 7 X 10; 

 8X7; after Atkinson, 1905, and Moller, 1901.) 



rotic in age and perithecial formation takes place on special prosenchymatic 

 outgrowths which break through the hard stroma. The simplest forms, 

 as Balansia Hypoxijlon, are directly connected to Ophiodotis raphidospora. 

 In the Southern states, B. Hypoxylon is parasitic on various grasses and 

 surrounds the stems with a plectenchyma, fleshy when young, sclerotic in 



