DISEASES OE TREES AND SHRUBS. 69 



HACKBERRY. 



Leaf -spot (Cylhidrosporium defoliatum Heald and Wolf, 32). — The 

 common hackberry of this region (Celt is laevigata Willd.) is 

 quite generally affected with a serious leaf blight which first produces 

 irregular gray blotches 1 to 2 cm. in diameter. These blotches some- 

 times coalesce and involve a large part of the leaf. (PL XIV, fig. 1.) 

 In early stages of the disease the adjacent leaf tissue may remain 

 green, but later a considerable amount of yellowing is produced, and 

 the affected leaves fall from the tree. 



The acervuli are amphigenous, but more abundant upon the upper 

 surface, 60 to 75 fi, immersed. (PI. VI, fig. 10.) The spores accu- 

 mulate on the surface of the leaf, where they are visible as minute 

 white tufts. The spores are hyaline, cylindrical, straight, or curved, 

 30 to 42 by 3 to 3.5 /*, and three to five septate. (PI. VI, fig. 9.) This 

 species is clearly distinct from Cylindrosporium celtidis Earle, which 

 has been described as forming small spots on C. laevigata in Ala- 

 bama (11). 



Specimens collected: (1) On Celiis laevigata Willd. — New Braunfels, 1673; 

 Austin, 1728, 1905 (type specimen); Elgin, 1890; Bastrop, 2049; Lockhart, 

 2073 ; San Marcos, 2099 ; Cotulla, 2180 ; Luling, 2256 ; Seguin, 2317 ; Georgetown, 

 2377; Victoria, 2509; Cuero, 2578; Stockdale, 2615; Gonzales, 2689; Flatonia, 

 2709; Yoakum, 2771. (2) On Celtis reticulata Torr — Beeville, 1855; Sabinal, 

 1975. 



Leaf -spot (Ramularia celtidis Ell. and Kellerm.). — Very numerous 

 small white spots form on the leaves. They are circular in outline 

 and about 2 mm. in diameter. The margin is brown or yellow and 

 slightly raised. 



Specimens collected: (1) On Celtis reticulata Torr. — Austin, 464; Beeville, 

 1814; Luling, 2265; Gonzales, 2690; Kennedy, 2835. (2) On C. laevigata 

 Willd.— Austin, 1539 ; Lockhart, 2062 ; Georgetown, 2355 ; Hallettsville, 2779. 



Mistletoe (Phoradendron flavescens (Pursh.) Nutt,). — This para- 

 sitic plant is present on the hackberry throughout the territory cov- 

 ered by this survey. It is often so abundant that the winter aspect 

 makes the tree appear in full foliage. 



Powdery mildew (Uncinida polychaeta B. and C). — The mycelium 

 forms a white, felty coating on both leaf surfaces, generally forming 

 patches and not covering the entire leaf. 



Specimens collected: On Celtis reticulata Torr. — Austin, 415; Georgetown, 

 2392 ; Cuero, 2587. 



HAWTHORN. 



Blotch (Hendersonia foliorum, Fckl.). — On the leaves of the haw- 

 thorn (Crataegus spp.) large, brown, irregular blotches appear, and 

 on these blotches black dots (the pycnidia) are formed. Each 



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