May, 1909.] The Catalpa Leaf Spot. 509 



THE CATALPA LEAF SPOT.* 



J. B. Parker. 



On October 11, 1908, the writer collected from a catalpa tree 

 growing upon the campus of Ohio State University, a number of 

 leaves affected by the leaf spot fungus so prevalent upon this 

 tree. A few of these spots bearing fruiting bodies thought at the 

 time of collection to be those of a species of Phyllosticta were 

 killed and hardened in alcohol preparatory to imbedding in 

 paraffin. While yet in the alcohol this material was examined 

 under the low power of the microscope which revealed upon 

 some of these spots fruiting bodies smaller and lighter in color 

 than those of Phyllosticta, which were present also upon other 

 spots. When sectioned and stained these smaller bodies proved 

 to be perithecia containing S-spored asci in various stages of 

 development. This discovery led to a more careful study of the 

 remainder of the material collected and to a comparison of this 

 with specimens of leaf spot fungi of the catalpa found in the 

 herbarium of the late Dr. W. A. Kellerman. As a result of this 

 study, the writer is of the opinion that the fungus is a new species 

 belonging to the genus Didymosphaeria and herewith submits 

 the following description: 



Didymosphaeria catalpae n. sp. Perithecia very small, scattered, 

 imbedded in the tissue of the leaf, pyriform to nearly spherical, varying in 

 width from 48 — 104 mic. and in depth from 64 — 140 mic. Ostiolum 

 broadly conical, erumpent. Asci 8-spored, cylindrical, usually somewhat 

 curved', paraphyses fev\^ or wanting. Spores oblong-elliptical, hyaline or 

 yellowish, imiseptate, constricted in the middle 9.6 — 13 x 3 — 4 mic. 



Occurs in leaf spots upon Catalpa sp. the ostiola appearing 

 upon either or both surfaces of the leaf. 



In the herbarium were found specimens of two species of 

 imperfect fungi upon Catalpa leaves, Macrosporium catalpae 

 E & M on material collected by J. A. Jack, Jamaica Plain, Mass., 

 August 20, 1890, and Phyllosticta catalpae E & M collected by 

 H. W. Ravenel, Aiken, S. C, July, 1904. The comparison of this 

 herbarium material with that secured upon the university 

 grounds led to the discovery of conidial spores very similar to 

 those of Macrosporium catalpae upon the latter and also upon 

 that labeled Phyllosticta catalpae (Fig. 1, 2, 3). It revealed 

 also pycnidia upon the specimens labeled Macrosporium catalpae 

 similar to those upon specimens labeled Phyllosticta catalpae 

 and to those upon the leaves obtained upon the university 

 grounds. But upon none of the herbarium specimens did the 

 writer find perithecia. It may be of significance to note that the 

 material secured upon the university grounds was collected just 

 before frost fell and that only the latest developed spots bore 

 perithecia. 



* Contribution from the Botanical Laboratory of the Ohio State 

 University, XLV. 



