Oct., X9i3-Mar,, 1914 
Illustrations 
VII 
Page 
longitudinal view of a young sporophore on Quercus tex- 
ana from Texas, showing the fibrous, nongranular nature 
of the context. Fig. 5.— Polyporus fulvus Fries: Median- 
longitudinal view of a sporophore on Quercus sp. from 
Sweden, showing the granular core characteristic of P. 
dryophilus. Fig. 6.— Polyporus vulpinus: Median-longi¬ 
tudinal view of sporophore on Populus sp. from Sweden, 
showing the granular core characteristic of P. dryophilus. 
Fig. 7.— Polyporus dryophilus: Front view of the appla- 
nate type of a sporophore on Populus tremuloides from 
Colorado, showing the faint zones on the pileus where the 
hairs have disappeared. Fig. 8.— Polyporus dryophilus: 
Median-longitudinal view of sporophore on Populus tre¬ 
muloides from Colorado, showing the granular core origi¬ 
nating between the sapwood and bark and extending 
into the center of the sporophore. 250 
Pirate XXII. Fig. i.— Polyporus dryophilus: Radial-longitudinal view of 
the rot occurring in Quercus sp. from Furope and said to 
be the rot produced by P. dryadeus. Fig. 2.— Polyporus 
dryadeus: Cross section of a small root of Quercus alba from 
Maryland, showing the mottled appearance of the diseased 
wood in the middle stages of the rot. Fig. 3.— Polyporus 
dryophilus: Radial-longitudinal view of the rot appearing 
in Quercus alba from Arkansas, showing the advancing 
line of rot in a branch. Fig. 4.— Polypoms dryadeus: Up¬ 
per surface of a sporophore on roots of Quercus texana from 
Texas, showing the rough tuberculate pileus. Fig. 5.— 
Polyporus dryadeus: Rot occurring in an apparently sound 
root of Quercus alba from Virginia, showing cross section 
of a diseased root immediately adjacent to the point of 
attachment of a large sporophore of P . dryadeus , 1 foot high 
and 1 foot wide. Fig. 6.— Polyporus dryadeus: Cross sec¬ 
tion of a diseased root of Quercus alba from Virginia, show¬ 
ing the nearly sound, living upper half of the root and 
the badly diseased lower half. 250 
XXIII. Parts of sweet-potato plants, showing the presence of 
pycnidia: A, On the stem just above the ground; B , on 
the root. 274 
XXIV. Portion of sweet-potato vines several feet from the hill, 
showing the results of a natural infection of the foot-rot 
fungus. 274 
XXV. Microscopic characters of the foot-rot fungus: A , Section 
through a pycnidium on the root; B, section through a 
pycnidium on the stem; C, hyphae, from artificial cul¬ 
ture; D and E , chlamydosporelike bodies found on the 
host and in some culture media; F, pycnospores; G, 
club-shaped bodies often found in pycnidia; H, ger¬ 
minating pycnospores. 274 
XXVI. Two sweet-potato plants in pots, demonstrating the parasit¬ 
ism of the foot-rot fungus: A, Inoculated; B, not inocu¬ 
lated. 274 
XXVII. Nine-day-old cultures on synthetic agar: A, The conidial 
stage of Diaporthe batatatis; B, Plenodomus destruens .... 274 
