DISEASES OF TREES AND SHRUBS. 67 



the acervuli of the fungus. In a few cases the acervuli may be found 

 on the upper surface. 



The spores are very narrow, cylindrical, hyaline, continuous, 

 straight or slightly curved, 15 to 24 by 0.75 to 1 /m. 



Specimen collected: On Ulmus crassifoUa Nutt.— Austin, 307 (type specimen). 



Mistletoe {Pkoradendron flavescens (Pursh.) Nutt.). — The small- 

 leaved elm {Ulmus crassifoUa) is one of the many trees attacked by 

 mistletoe. 



Specimen collected : On Ulmus crassifoUa Nutt. — Llano, 1737. 



Powdery mildew {Unc inula sp.). — Powdery mildew^ was collected 

 in a single locality on the cork-winged elm (Ulmus alata). It was 

 found only in the conidial stage and was not abundant. Since two 

 species of Uncinula have been described for this host, a definite spe- 

 cific determination can not be made. 



Specimen collected: On Ulmus alata Miclix. — Llano, 1753. 



ENGLISH IVY. 



Anthracnose [C olletotrichunh gloeosporioides Penz. var. hederae 

 Pass.). — Irregular, brown, raised, definite-margined areas are formed 

 on the leaves of the English ivy {Hedera helix L.). Often they are 

 confined to the tips of the lobes, but at times they are central. The 

 acervuli are formed abundantly over the entire diseased areas. 



Specimens collected : San Antonio, 1408 ; Gonzales, 2685 ; Flatonia, 2747. 



Leaf -blight {Phyllosticta concentrica Sacc). — This disease begins 

 on the leaf tips or centrally and results in the formation of dark- 

 brown, dead areas which may extend until the whole leaf is involved. 

 Some spots have a blackish tinge, due to the numerous pycnidia, 

 which in some cases are arranged so as to show concentric zonation. 

 The spores are ovoid, 10 by 7 /i, hyaline, guttulate, and embedded in a 

 mucilaginous matrix. This blight in one locality was observed to 

 have destroyed about half the foliage; so it is the cause of serious 

 harm. 



Specimens collected:. Austin, 1313; New Braunfels, 1667; Stockdale, 2637. 



Leaf-spot {Ramulana hedericola Heald and AYolf, 32). — Large 

 irregular spots, grayish brown above and brown below, appear on the 

 leaves. The margin of the diseased area is elevated, with the fungus 

 fruits on the upper leaf surface. Conidiophores 60 to 120 by 4 /x, 

 septate. Conidia clear, 9 to 15 by 2.5 ju. (PI. V, fig. 5.) 



Specimen collected: San Marcos, 2130 (type specimen). 

 226 



