106 
Mycologia 
On living leaves of Rhus Toxicodendron and other species. 
Exsicc. N. Am. Fungi 1898, 244'/ a & b; Fungi Col. 44^, 1350, 
2635, 4429, 4430, 4734. 
I have had the opportunity of studying what might be regarded 
as two of the cotypes as well as specimens from several herbaria 
and several collections of my own made in widely separated 
localities, and find them all remarkably uniform in maculae and 
acervuli and varying in conidia. The synonymy is quoted to il- 
lustrate the difficulty of determining in some cases whether there 
is a proper pycnidium. Curtis, Peck, Ellis, and Martin took this 
plant to be a Septoria and the dark cells overlying the acervuli 
might be supposed to be part of a pycnidial wall. It is to be 
noticed that it was described both as a Septoria and a Gloeo- 
sporium by the same authors. It also illustrates another diffi- 
culty — that of determining the genus by the spore-form. In a 
section through a single spot cutting three acervuli there were 
conidia exhibiting the following variations ; 
21 X 4 i-septate 
18 X 5 • ■ • • o-septate 
Conidia from extreme, isolated, examples might very well place 
this species in Marsonia, or Septogloeum, or Cylindrosporium. 
Four of the Fungi Col. numbers are labeled Marsonia as in the 
above synonymy, but in one of them, on Rhus diversiloba, the 
spores in my specimen are mostly nearly 50 ju., obscurely septate, 
and one — the longest measured — was 78 X 3/^ in which, if there 
were any septa, they were quite obscured by the nucleation. In 
1893, Ellis stated that he had reexamined Gloeosporium Toxi- 
codendri Ellis & Martin and found that the spores (“ 12-15 X 
5-6 /x”) had been erroneously described in Jour. Myc. I: 115. I 
have, however, seen short spores not far from these figures, but 
the average spore of a large number of studies certainly places 
this plant in Cylindrosporium. 
51 X 3 /^ 
60 X 3/^ 
3-septate 
2-septate 
