132 BOTANICAL GAZETTE [FEBRUARY 
Boyce (2) first observed the pycnia of Peridermium pyriforme 
on Pinus ponderosa near Castella, Shasta County, California, 
July 21, 1916. He states that “the pines are probably infected in 
the summer or fall of one season, pycnia do not appear until the 
summer of the next season at the earliest, while mature aecia are 
produced in the late spring or early summer of the third season.” 
Hepccock, BETHEL, and Hunt (6) state that the pycnia of 
Peridermium pyriforme are borne on areas of the bark of pines 
contiguous to the aecia and preceding them by one year. They 
are produced in the portions most recently invaded, commonly on 
the trunks and limbs. In both P. pyriforme and P. filamentosum 
the pycnia most frequently appear at a date later in the season 
than the aecia. 
Hepccock and Lonc (7), from field observations during a period 
of four years, find that in the swellings of Peridermium cerebrum or 
Pinus virginiana the pycnia precede the aecia one year, instead of 
preceding them during the same spring. In other words, the 
pycnia and aecia occur during alternate years, and two years is 
the time required for a life cycle of all forms of spores of the rusts. 
DopcEe and Apams (5) studied material of P. cerebrum on — 
Pinus rigida and P. virginiana, and our observations indicate that 
there is an alternation of aecia and pycnia. 
We have not seen in any instance spermatial hyphae developing in the 
tissue overlying that in which the aecidia are being formed. Cross-sections 
of the Virginia material developing both spermatial and aecidial fructifications 
on the same gall show that there is no sharp line of demarcation between the 
two. In one burl there was a space of only 700 yw separating them. 
SHIRAI (8) has shown by culture experiments the connection of 
Peridermium giganteum and Cronartium quercuum, which has been 
considered the same as the form of P. cerebrum in North America. 
In an illustration he shows the extended pycnial layer in the tissue 
overlying the aecia, and states: 
e spermagonia of this fungus are formed in the month of January in 
the intercellular spaces between the corky bark and the corticial parenchyma. 
: n consequence of the formation of the spermagonia and the subsequent 
conckine of the corky bark, the pressure of the latter on the i inner bark greatly 
lessens, and tl f the aecidial | 
J 
hed P tissues. 
