36 BULLETIN 957, U. S. DEPARTMENT OF AGRICULTURE. 
(143, 144) that squirrels ate the swollen bark from the infected parts 
of the branches. (PL III.) They undoubtedly run over fruiting 
cankers and pick up seciospores on their fur and feet. Porcupines 
may act in the same manner. Birds undoubtedly carry these spores 
to some extent, and as in the secial season they begin nesting and 
largely remain in the same locality they, too, act only as local carriers. 
Some indications have been noted where a road traverses a narrow 
valley, or a narrow clearing in a forest, that automobiles create drafts 
which carry spores to some distance along the highway. It seems 
entirely possible for steam trains and electric cars to do the same 
thing. 
POSSIBLE AUTGECISM OF THE .#} CIO SPORES. 
The possible autoecism of the seciospores of Cronartium ribicola has 
been considered. As early as 1913 field observations were made with 
this point in view, but no evidence of the spread of the fungus directly 
from pine to pine was found. 
The question whether seciospores of other stem-inhabiting pine 
Peridermiums are capable of infecting pines has received considerable 
attention. In 1907 Liro (82) stated that he had made 169 inocula- 
tions of Pinus sylvestris with seciospores of Peridermium pini from 
the same host. No infections resulted. In 1914 Haack (48) stated 
that he had made similar inoculations and obtained abundant infec- 
tions. His experiments were performed out of doors, with no pro- 
tection from natural infection and with trees which already were 
naturally infected ; hence, his results are worthless. In 1913 Meinecke 
(95) made successful inoculations with seciospores of "Peridermium 
liarknessii" upon Pinus radiata under controlled conditions. Later 
(96) he changed the name of the fungus to Peridermium cerebrum and 
reported that he had successfully inoculated Pinus radiata with 
seciospores from P. radiata and from P. attenuata; and P. muricata 
with seciospores of P. cerebrum from P. radiata. 
In 1915 Hedgcock (51) successfully inoculated trees of Pinus 
ponderosa var. scopulorum, P. contorta, P. saMniana, P. caribaea, 
P. mariana, P. pinea, and P. halepensis with seciospores of "Peri- 
dermium Jiarknessii^ from P. contorta. He has also successfully 
inoculated P. ponder osa and P. virginiana with seciospores of U P. 
JiarknessiV from P. ponder osa. 
In 1918 Klebahn (73) published the results of successful inocu- 
lations made by him with seciospores of Peridermium pini upon 
young twigs of Pinus sylvestris, both with and without wounds, 
under controlled conditions. These results throw doubt on the 
strict heteroecism of the seciospores of all the stem-inhabiting pine 
Peridermiums. 
The following tests have been made with the seciospores of Cro- 
nartium ribicola: Klebahn (68, 70) repeatedly inoculated young 
