Abstract
1. In the present experiments have been observed the points of penetration of several Peronosporaceous fungi inoculated on the under surfaces of the leaves of their hosts and other plants.
The fungi and their hosts on which the inocula were collected are as follows:
Peronospora Brassicae GÄUM. Brassica chinensis L., B. chinensis L. var. KOMATSUNA MATSUM. et NAKAI, B. chinensis L. var. oleifera MAKINO, B. pekinensis RUPR., B. oleracea L., B. Rapa L.
P. parasitica (PERS.) FR. Capsella Bursa-pastoris MOENCH.
P. sp. Cleome spinosa JACQ.
P. Stellariae-uliginosae SAWADA. Stellaria uliginosa MURR.
P. Viciae sativae GÄUM Vicia sativa L.
P. Trigonotidis S. ITO et TOKUNAGA Trigonotis peduncularis BENTH.
P. variabilis GÄUM Chenopodium album L. var. centrorubrum MAKINO
P. Spinaciae LAUBERT Spinacia oleracea L.
Bremia Saussurae SAWADA Hemistepta carthamoides O. KUNTZE
Plasmopara nivea (UNGER) SCHRÖT. Cryptotaenia japonica HASSK.
P. viticola (BERK. et CURT.) BERL. et de TONI Vitis Thunbergii SIEB. et ZUCC. var. typica MAKINO
Pseudoperonospora Humuli (MIYABE et TAKAHASHI) WILSONHumulus japonicus SIEB. et ZUCC.
2. In all of the eight species of the genus Peronospora, penetrations were observed to occur on the whole through the boundary line of the epidermal cells. Penetration through the stomata or through the free surface of the epidermal cells did occur in some cases, though in a very small proportion. For instance, on inoculating Brassica chinensis L. var. KOMATSUNA MATSUM. et NAKAI with Peronospora Brassicae GÄUM. collected from this plant, the ratio of the penetrations through boundary line, stomata and free surface were calculated to be 95.6-98.9%, 0.8-3.9% and 0.0-0.8% respectively in experiments repeated three times.
3. The points of penetration of Peronospora Brassicae GÄUM. are not affected by the removal of the wax on the leaves of its hosts. Also those of P. Brassicae GÄUM., P. variabilis GÄUM. and P. Spinaciae LAUBERT were ascertained to be in different to the grade of maturity of the leaves of their hosts.
4. Bermia Saussurae SAWADA also mostly penetrates through the boundary line of the epidermal cells. But the stomatal penetrations seem to be considerably frequent, though the percentage was not calculated.
5. In contrast with the case of the Peronospora species, penetrations of Plasmopara viticola, Plasmopara nivea and Pseudoperonospora Humuli were observed to occur only through stoma.
