DISEASES OF TREES AND SHRUBS. 57 



Sore-shin (Corticium vagvm B. and C. var. solani Burt). — No 

 field notes are at hand regarding the extent of the losses caused by 

 this organism upon the young plants. It is probably generally 

 present and the cause of a very considerable loss in warm, rainy 

 springs. 



Specimen collected: Austin, 2895. 



DISEASES OF TREES AND SHRUBS. 

 ALTHAEA. 



Root-rot (Ozonium ommvorurrb Shear). — The fungus which causes 

 this trouble on althaea {Hibiscus syriacus L.) is the same as the one 

 which produces the root-rot of cotton. The attendant symptoms are 

 essentially similar. The disease was observed only in nurseries, where 

 it killed all the plants in certain sections of the nursery rows. 



Specimens collected : Austin, 1924 ; New Braunfels. 



ASH. 



Leaf -spot (Cercospora fraxinites Ell. and Ev.). — The spots caused 

 by this fungus on the leaves of ash {Fraxinus spp.) are subcircular 

 or somewhat irregular, dark gray above, with many minute black 

 heaps of conidia and conidiophores, and are margined by a zone of 

 brown fading out into the green tissue which may show a certain 

 amount of chlorosis; the affected areas are pale brown below with a 

 slightly darker, definite margin, and show fewer and less conspicuous 

 conidial tufts. The spots are 4 to 10 mm. in diameter. Sometimes 

 they are confluent, causing larger dead areas along the margins of the 

 leaflets or removed from the margin. It is stated in the original de- 

 scription of this species (16) that the spots are 3 to 4 mm. in diameter, 

 but the agreement of spore measurements and other characters indi- 

 cate that our species is C. fraxinites Ell. and Ev. 



At the time specimens were collected, September 1, little or no de- 

 foliation had resulted, but nearly all leaves were affected, each leaflet 

 showing 1 to 13 spots. 



Specimen collected: Victoria, 2340. 



Leaf-spot {Cylindrosporium viridis Ell. and Ev.). — On the upper 

 surface of the leaf the numerous spots are dark purple in color, rang- 

 ing in diameter from 1 to 4 mm. with a definite margin. The affected 

 areas are more dilute on the under surface, often brownish, and con- 

 cealed in part by the abundant heaps of white or pinkish spores. 

 The acervuli are immersed, globular or somewhat flattened, 150 fi 

 or less in diameter, and become erumpent only on the lower surface. 



According to the original description (19) the acervuli are from 

 three to six in number on each spot and open above. The spores 



226 



