132 ILLINOIS ACADEMY OF SCIENCE 



caused by Phyllosticta is due to a weakening or killing of the 

 leaf-tissue by the mycelium, which spreads throughout the 

 leaf. When conditions are favorable, the spots develop rap- 

 idly and the greater part of the leaf from the margin to the 

 mid-rib may become involved. Sometimes the spots are brown, 

 giving the appearance of sunburn, or again they may be of 

 yellowish color, or sordid-white, or perhaps gray, with a red- 

 dish-purple margin which may be concentrically zonate. The 

 center of the spot often falls out, and eventually, when af- 

 fected to such ail extent that they can no longer function, the 

 leaves fall, thus weakening the vitality of the tree. Instead 

 of being borne on conidiophores as in Cercospora, the conidia 

 are produced in pycnidia. They are usually en the upper sur- 

 face of the leaf, though sometimes below, and appear as tiny 

 black specks when large enough to discern with the aid of a 

 lens. They may occur singly or in clusters, and may be im- 

 mersed, erumpent or superficial. When immersed a beak 

 pierces the epidermis, thus facilitating the escape of conidia. 

 The pycnidia are lenticular to globose, usually brown or black, 

 opening by a pore or ostiole which is often dark-bordered. 

 The conidia are hyaline, usually ovate to elliptical, though 

 sometimes spherical, and they vary in length from 2 to 60 /*. 

 The perfect stage of this fungus is known in but few cases. 



It has been the custom when creating new species to desig- 

 nate as new those forms which have never been reported on 

 the particular host or any genus of the same family, and which 

 are distinct from any form on a related host. In working over 

 some 50 different forms, I have found 15 which are distinctly 

 new species. However, I am somewhat hesitant to describe 

 these as Phyllostictas, rather than Phomas, since I believe 

 there is no tenable distinction between these two genera. They 

 are alike in conidia and pycnidia, and these parts seem to me 

 to be the most characteristic. The general nature of the spots 

 cannot serve as distinguishing features since they are both 

 definite and indefinite on the leaves, nor does it seem justifiable 

 to make the location of infection of a plant a basis for dis- 

 tinguishing species. 



