OF ARTS AND SCIENCES. 321 



was found by Mr. Faxon in July, but at the time of my visit, the sec- 

 ond week in August, not a trace of the fungus was to be found, either 

 on the livinw or fallen leaves of Ledum. 



The first specimens received from Mr, Faxon were collected on 

 Mt. Washington in June. On the upper surface of the leaves were 

 small blood-red pustules, which a microscopic examination showed to 

 be undistinguishable from the teleutosporic condition of Ghrysomyxa 

 Ledi (A. & S.). In July other specimens were received fiom Mr. 

 Faxon wiiere no teleutospores were found, but there was an abundance 

 of a uredo form which presented two different aspects. On the upper 

 side of the leaves, in dark discolored spots, a small number of sori 

 were grouped, generally more or less circularly. Sections show'cd 

 orange-colored spores with decidedly roughened epispores surrounded 

 by a rim of densely ^lacked cylindrical filaments composed of several 

 cells, the whole surrounded by the ruptured epidermis in form of a 

 cup. The spores were produced in small numbers in chains, but at 

 maturity became free, and were then globose or broadly elliptic, meas- 

 uring 24-38 ft by 20-26 /x. This epiphyllous form is certainly the 

 Uredo ledicoJa, Peck, of which, through the kindness of Mr. Peck, I 

 have been able to examine an authentic specimen. 



In some sections I also found sori on the under side of the leaves. 

 They could scarcely be detected by the eye, owing to the densely 

 tomentose character of the under side of the leaves ; but I afterwards 

 noticed that, when small yellowish spots were seen on the upper sur- 

 face of the leaves, the sori could be found beneath. In a compara- 

 tively small number of cases sori were found on both sides of a leaf, 

 but generally this was not the case. In Mr. Faxon's collections the 

 epiphyllous form was more abundant than the other. The two may 

 be equally abundant in nature; but as the epi])hyllous form is much 

 the more striking to the eye, it naturally follows that the epiphyllous 

 form would lie found more abundantly in collections. In general, the 

 developments of the epi- and hypo-phyllous forms was the same, but 

 there was a constant difference in the mature forms. The sori of the 

 hypophyllous form, instead of being in the shape of widely-opened 

 cups, scarcely sunk at all below the level of the epidermis, looked 

 more like partially immersed conceptacles with slightly contracted 

 orifices, whose outer portion projected beyond the epidermis. The 

 spores also were distinctly narrower and more acutely elliptical, meas- 

 uring 24-31 ji by 12-19//, and the epispore was less rough. 



I think that there can be no doubt that the hypophyllous form is 

 the uredo of Chrys. Ledi, as it answers closely to the descriptions of 



VOL. X-X. (n. S. XII.) 21 



