Abstract
The writer has made an investigation on the histology of hypertrophied leaves of Camellia Sasanqua THUNB. caused by Exobasidium Camelliae SHIRAI var. gracilis SHIRAI.
The hymenium of the causal fungus developing usually on the under surface of the affected leaves appears at first in the intercellular spaces of the mesophyll and is covered with two to seven layers of cells under the epidermis. The overlying tissue ruptures, with the maturity of the hymenium, becoming a membranaceous piece, which usually remains attached to the margin of the leaf (Fig. 2).
Both hypertrophy and hyperplasia, inducing the changes in the proper arrangement of cells, occur in the affected leaves and consequently various layers of cells lose their individuality. The changes in the arrangement of cells in the pathological tissue are recognized partially to be caused by osmotic pressure.
The new formation of such vascular bundles, as found in the cortex of hypertrophied buds of Camellia japonica, is not discovered in the affected leaves by the present disease, but some of the endings of the vascular bundles extend towards the hymenium of the causal fungus (Plate III, E). This mechanism also seems to serve for the nutritionsupply of the host to the causal fungus.
