May, 1909.] 
The Catalpa Leaf Spot. 
5°9 
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 few or wanting. Spores oblong-elliptical, hyaline or 
yellowish, uniseptate, 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. 
