Abstract
1. Conidia of Piricularia oryzae Cav. are unicellular, small spheres in their primary stage of development and expand into oval form dividing into two cells. The lower cells of the pairs remain scarcely changed, while the upper ones lengthen and divide, giving forth mature bottle-shaped spores with two septa.
2. Conidia in water drops upon living rice sheath or upon onion-scale epidermal strips, immersed for a while in alcohol and washed with running water, develop germ tubes from the apical cells, forming appressoria. The contents of the central and basal cells are promptly transferred to germ tubes and appressoria. Then the basal, central and apical cells lose their contents, becoming shrivelled successively in this order.
Conidia in water drops upon slide glass generally develop germ tubes first from apical cells, next from basal ones and lastly but rarely from central ones. Translocation of contents of three cells is slow and the central cells seem to be disposed to keep the contents for a longer period.
Conidia in rice-straw decoction produce germ tubes in succession from three cells as in water drops and the germ tubes extend into long hyphae branching profusely. Translocation or utilization of the spore contents is far slow compared with that in the above two cases, apparently because the germ tubes are nourished by the decoction.
3. Among three cells of conidia, the apical cells are generally the shortest-and the central ones the longest-lived, but the difference is not so conspicuous. No particular translocation and accumulation of contents into one of the three cells is observed and no chlamydospores or chlamydospore-like structures are formed.
