Arthur and Kern: North American Peridermium 137 
knowledge that the Cronartium on Quercus occurs also in south- 
ern Mexico has greatly assisted us in coming to the present con- 
clusion. 
Considerable advance has been made also in the knowledge of 
the development of the aecial stage. With the aid of Dr. C. 
L. Shear the existence of the pycnial stage has been demonstrated, 
and a brief technical description has been included in the above 
diagnosis. Dr. Shear also points out that the fungus seems to 
have a biennial development, at least he is sure in some cases that 
only pycnia develop the first season following infection. Two 
years would thus be required for the development of the aecia. 
Host Index to the Species of Peridermium on the Species of Pinus 
australis 
carneum 1 1 
austriaca 
Comptoniae 15 
Banksiana 
cerebrum 16 
Fischeri 3 
pyriforme 13 
contorta 
cerebrum 16 
filamentosum 12 
divaricata 
cerebrum 16 
pyriforme 13 
echinata 
cerebrum 16 
Comptoniae 15 
intermedium 8 
Elliotii 
carneum 11 
filifolia 
guatemalense 10 
gracile 7 
“ heterophylla ” 
carneum 11 
inops 
Comptoniae 15 
insignis 
californicum 5 
cerebrum 16 
Jeffreyi 
filamentosum 12 
maritima 
Comptoniae 15 
mitis 
cerebrum 16 
intermedium 8 
montana 
Comptoniae 15 
Murrayana 
cerebrum 1 6 
filamentosum 12 
fnontanum 4 
pyriforme 13 
oocarpa 
cerebrum 16 
palustris 
carneum 11 
cerebrum 16 
patula 
cerebrum 16 
ponderosa 
cerebrum 16 
Comptoniae 15 
filamentosum 12 
pyriforme 13 
pungens 
acicolum 6 
pyriforme 13 
radiata 
californicum 5 
cerebrum 16 
rigida 
acicolum 6 
cerebrum 16 
Comptoniae 15 
delicatulum 1 
Rostrupi 9 
sabiniana 
cerebrum 16 
scopulorum 
cerebrum 16 
filamentosum 12 
montanum 4 
pyriforme 13 
“ serotina ” 
carneum 11 
Strobus 
Strobi 14 
“ Strobus ” 
cerebrum 16 
sylvestris 
Comptoniae 15 
Fischeri 3 
Taeda 
carneum 11 
cerebrum 16 
Comptoniae 15 
virginiana 
cerebrum 16 
Comptoniae 15 
inconspicuum 2 
indet, spp. 
cerebrum 16 
delicatulum 1 
pyriforme 13 
