DISEASES OF TREES AND SHRUBS. 61 



Leaf-spot {PhyJlosticta humelii folia Heakl and Wolf, 32).— This 

 causes the formation of definite, pale-brown spots on the leaves. 

 These spots vary in diameter from 3 to (> mm. when circidar or siib- 

 eircular, but often the areas have fused so that much larger, irregu- 

 lar spots are produced. The color is less intense on the lower sur- 

 face. Numerous black pycnidia, ranging from 125 to 150 ju,, open 

 to the upi>er surface. The spores are globular, granular, with one or 

 more guttultc, 9 to 15 ju, in diameter. In severe cases half of the leaf. 

 tissue may be involved. 



Specimens collected: Austin, 1549 (type specimens) : .3032. 



Sooty mold {Fumago vagans (?) P.). — The interlacing filaments 

 give the effect of a black crust on the entire upper surface of the leaf. 

 Specimen collected : Austin, 253. 



BUTTONBUSH. 



Leaf-spot {Ramularia ce-phalanthi (Ell. and Kellerm.) Heald). — 

 This fungus on the buttonbush {C ephalantkus occiclentalis L.) pro- 

 duces numerous circular, brown spots 0.5 to 2 mm. in diameter, sur- 

 rounded by a narrow, slightly elevated, darker brown border, which 

 is in turn surrounded by a zone of bright red, 1 to 2 mm. wide, ir- 

 regular margined, and fading out into the green. The spots are uni- 

 formly brown on the under surface. Conidia are produced only 

 when the brown centers become somewhat gray. The spots may be 

 very abundant and become confluent, causing the death of large 

 areas of the leaf, or considerable chlorosis may precede the browning. 



The size of the spores and the general symptomatology indicate 

 that the fungus is Cercospora cephalanthi Ell. and Kellerm. (23), 

 but the formation of the spores in chains (PI. V, fig. 4) places it with 

 Ramularia. Our specimens show spores which are apparently ma- 

 ture, 18 to 30 by 3 /i, and hyaline or faintly smoky. The change in 

 size and color given for mature specimens (17) is probably based on 

 the examination of a true Cercospora. 



Specimens collected: Uvalde, 1930; Cotulla. 2148. 



Leaf -blight {Cercospora pemiciosa Heald and Wolf, 32). — When 

 this disease is present the entire foliage of the tree is seriously 

 affected. Isolated spots are about 1 cm. in diameter, reddish brown, 

 with a darker border. Often the spots have narrow rings of this 

 darker brown tissue, rendering them zonate. 



Most commonly these spots are irregular in outline, as the diseased 

 areas have fused, causing a large part of the leaf to become dry. 

 The lower surface of the leaf is much more dilutely colored. On 

 the upper surface the profusion of conidiophores and conidia renders 

 the spots grayish. The conidiophores are densely fasciculate, clear 

 or dilutedly colored, 40 to 50 by 3 to •i /x. The spores are clavate, 



226 



