188 BOTANICAL GAZETTE [MARCH 
which has in some manner accidentally become mixed with Drum- 
MOND’s arctic collections while they were in the process of being 
mounted at the museum. This seems all the more probable 
when it is noted that the handwriting on the labels is the same as 
that on a great many of the other specimens from the same museum. 
It would seem, therefore, quite probable that Systremma Ulmi 
does not occur at all in America. Although ELiis and EVERHART 
place the causative organisms of the two diseases in the same 
genus, they express a caution against confusing the two, stating 
that although they have spores essentially the same they differ 
very markedly in other characteristics. In spite of the fact that 
the external appearances of the two spots seem quite similar to 
the casual observer, as soon as one sections them the very marked 
differences between the two fungi become apparent. Fig. 10 
represents a section through the stroma of Systremma Ulmi. It 
will be seen that the black stroma, to which the external resemblance 
between the two forms is due, is in this case subepidermal, while in 
Gnomonia ulmea it is subcuticular only. In the Systremma the 
asci are produced in locules without true perithecial walls, which 
are imbedded in the stroma and open on the upper side of the leaf, 
while in Gnomonia the perithecia, truly sphaeriaceous in character, 
are located in the leaf tissue beneath the stroma and open on the 
under side of the leaf. Gnomonia ulmea, therefore, belongs to 
the Sphaeriales, while Systremma Ulmi belongs to an entirely 
different order, the Dothidiales. Although the asci and spores of 
the two differ but little in form, both are slightly larger in Sys- 
tremma than in Gnomonia. 
I have examined all available published exsiccati specimens of 
this fungus, as well as about 200 other specimens borrowed for 
purposes of examination and comparison from the Royal Botanical 
Gardens at Kew, and from the University of Geneva, and from a 
number of institutions and individuals in this country. The pub- 
lished exsiccati of this fungus examined were as follows: BERKELEY 
Brit. Fung. no. 192; V1zE Mic.-Fung. Brit. no. 277; CookE Fung. 
Brit., Ser. I, no. 184; Brrost and CavaRA Fung. paras. no. 73; 
Pottacci Fung. Longobardiae Exsic. no. 287; Saccarpo Myc. Ven. 
nos. 231 and 642; RouMEGERE Fung. Sel. Exsic. nos. 466 and 
