. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 24 BULLETIN 159^ U. S. DEPAETMEFT OF AGRICULTURE. After passing through the wall, the germ tube quickly expands to normal size. When 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 hyphse. No marked disorganization of the cell contents appears to result from this in- vasion until hyphae become very numerous. The actual time required for a
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 24 BULLETIN 159^ U. S. DEPAETMEFT OF AGRICULTURE. After passing through the wall, the germ tube quickly expands to normal size. When 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 hyphse. No 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- peziza medicaglnis and P. trifolii 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: Trifolium pra- tense by Pseudo- pe ziz a medica- ginis. — Inoculated leaves were de- colorized in two, three and five days after Inocu- 1 a t i 0 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 by Pseudopeziza trifolii.—A leaf inoculated on the plant on March 28, 1915, appeared to show penetration in 60 hours. Five leaves inocu- lated on December 4, 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.
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