24 
BULLETIN 759, T. S. DEPABTMEXT OF AGRICULTURE. 
After passing through the wall, the germ tube quickly expands to 
normal size. TVhen it reaches the center of the cell it usually divides 
(fig. 5) into two or three branches, which pass into the adjoining 
epidermal cells or down into the palisade layer. Cell walls do not 
appear to offer any obstruction to advancing hypha?. Xo marked 
disorganization of the cell contents appears to result from this in- 
vasion until hyphae become very numerous. 
The actual time required for a spore to germinate and transfer its 
contents to the germ tube inside the leaf has not been determined 
accurately, but in most cases it must be less than 12 hours at 18° to 
22- C. 
This description applies to the method of penetration of Pseudo- 
ptzlza medicaginis and P. trifoUi in their respective hosts. The 
following notes have been made of the penetration of germinating 
spores of these 
fungi in other 
reported hosts 
that have been 
available : 
Trifdlium pro- 
tense by Pseudo- 
peziza mcdica- 
gin is. — Inoculated 
leave? were de- 
colorized in two, 
three and fire 
days after inocu- 
1 a t i o n . After 
three days the 
host cells beneath 
many of the germinated spores had yellow granular contents. The yellow 
color made the exact relation of the germ tube to the cell impossible to deter- 
mine. In five days it could be observed that in the case of at least a part of 
these yellowed cells the germ tube had passed through the epidermal cell wall, 
but had not advanced far into the cell. 
Medicago sativa oy Pseudopeziza trifolii. — A leaf inoculated on the plant on 
March 2S ? 1915. appeared to show penetration in 60 hours. Five leaves inocu- 
lated on December 1. 1916. and decolorized four days later showed many yel- 
lowed cells beneath germinated spores. Suitable fragments were embedded 
and penetrations found in sections. The germ tube had not advanced beyond 
the first cell which it entered. 
Jledicaoo lupulina by Pseudopeziza medicaginis. — Four series of leaves re- 
moved from the plant were tried. Penetrations were noted in 23 hours at 22° C. 
Penetrated cells always show yellow granular contents. Even after 75 hours 
it was doubtful whether the germ tube had advanced beyond the first cell 
penetrated. 
Medicano lupulina by Pseudopeziza trifolii. — One series of leaves was removed 
from the plant. Penetrations were abundant and the penetrated cells* yellowed, 
Fig. 5. — Penetration of the epidermis of an alfalfa leaf by the 
germinating ascospores of Pseudopeziza medicaginis. X 800. 
