622 THE FUNGI WHICH CAUSE PLANT DISEASE 



flask-shaped, strongly constricted at the septa, olive, 40-60 x 



10-17 n. 



Circular leaf-spots are produced on violets. Spores are found on 

 the spots only when conditions are most favorable, i. e., in a humid 

 air. The parasitism of the fungus was demonstrated by inocula- 

 tion with spores on living leaves in distilled water. 



A. panax Whet.^^e 



Spots amphigenous, circular, becoming dingy white with a 



Fig. 420.— Alter- 

 n a r i a. Spores 

 and spore-bear- 

 ing stalks. Af- 

 ter van Hook. 



Fig. 421. — A. dianthi. S, Mycelium showing 

 branching and septation. 4> Showing my- 

 celium below stoma and hyphs emerging 

 through the stoma. S, Showing catenu- 

 late spores as borne upon hyphs. 6, Spores 

 showing shape, septation and catenulation. 

 7, A young cluster of hyphse. 8, An older 

 cluster of hyphse. After Stevens and Hall. 



reddish-brown margin, covering half the leaflet or less; hyphae 

 brown, septate, 5-7 n in diameter; conidiophores erect, tufted, 

 somewhat irregular, especially at the tips, brown,, septate, 100- 

 120 X 5-6 m; conidia brown, in chains of 5 or 6, elliptic to oblong, 

 45-65 X 15-20 fi. 



On ginseng causing leaf blight. 



A. dianthi S. & H.^" 



Spots epiphyllous, ashen-white, definite, circular. Conidiophores 

 cespitose from stomata, amphigenous, dark-brown, 1 to 4-septate, 

 erect, 1-25 from a stoma; conidia 26-123 x 10-20 n, clavate. 



