34 



Mycologia 



collection reported for Pennsylvania. The leaves were heavily 

 infected. Along a path for a distance of one fourth of a mile, 

 the Hydrangeas and Hemlocks were quite numerous. The Hem- 

 locks were infected with a Peridermium, which resembled P. 

 Peckii. Additional material of the Peridermium stage was col- 

 lected June 24, 1919. At this time the infection was just appear- 

 ing on the first leaves of the new growth. Inoculations with this 

 material was made the following morning in the greenhouse on 

 Hydrangea arborescens grandiflora and H. hortensis. Two other 

 species growing in the botanical garden were inoculated. H. 

 petiolaris and H. paniculata grandiflora, as well as a species of 

 Vaccinium. On July 7, 1919, mature uredinia were observed on 

 the leaves of H. arborescens grandiflora, a sterile, cultivated form 

 of the wild Hydrangea arborescens L. The results on the other 

 plants were negative. A visit was made to Bear Run, July 17, 

 1919, when mature uredinia were found developing on the leaves 

 of Hydrangea arborescens. An examination of the Vaccinium 

 spp., and of Agrimonia gryposepala, in the vicinity failed to re- 

 veal any infection. 



Compared with Peridermium Peckii this Peridermium shows 

 a close similarity. The pycnia are not so large, and do not ex- 

 tend between the walls of the epidermal cells so deeply. Aecia 

 when fresh are deep orange in color, and more elongated. The 

 aeciospores are more uniformly ellipsoid, and more finely verru- 

 cose, than those of P. Peckii. On the basis of cultural relations 

 a new combination is made. The morphological characters are 

 such as to identify this form as a new Peridermium and the fol- 

 lowing new name is proposed to represent this in the form genus 

 Peridermium with pycnia and aecia described as follows. 



Peridermium Hydrangeae (Berk. & Curt.) comb. nov. 



0. Pycnia amphigenous, usually hypophyllous, subcuticular, 

 abundant, inconspicuous, flattened, 74-112 /x wide, 80-145 J* broad, 

 19-32 fi high, extending slightly between the lateral walls of the 

 epidermis, frequently confluent. 



1. Aecia hypophyllous, in two rows, cylindric, deep orange 

 when fresh, 160-220 /x in diameter, I— 1.5 mm. high, dehiscent at 

 apex, also sometimes by side slits ; peridium colorless, with cells 

 slightly overlapping, the outer walls thin, the inner walls finely 



