The diseases and pests of the rubber tree . Fio. 8.—Ustulina zonata; fructification, x J. base of the stem. These plates are at first white and soft,but soon become grey or greenish-grey. In the tj^ical formthey are generally concentrically zoned or corrugated. Theythen harden and become purple-grey, and finally weatherto black ; in these later stages they bear scattered, miuute,black, slightly elevated points. After the plates havebecome hard they are at &st white internally, with a singlelayer of dark, oval, or globose cavities (Fig. 9); later theybecome black internally, and more or less ho
The diseases and pests of the rubber tree . Fio. 8.—Ustulina zonata; fructification, x J. base of the stem. These plates are at first white and soft,but soon become grey or greenish-grey. In the tj^ical formthey are generally concentrically zoned or corrugated. Theythen harden and become purple-grey, and finally weatherto black ; in these later stages they bear scattered, miuute,black, slightly elevated points. After the plates havebecome hard they are at &st white internally, with a singlelayer of dark, oval, or globose cavities (Fig. 9); later theybecome black internally, and more or less hollow. Whenold they are brittle, and easily crumble to pieces whenhandled. They are usually not more than about two milli-metres ROOT DISEASES 61 Though the fructification is, in general, more or less flatwhen it grows on the bark of Hevea, it may assume otherforms, especially if growing on an irregular surface. At thebase of the tree it often grows over irregular bark, or evenover soil, etc., and isthen thrown into irre-gular undulations,and may lack theconcentric crusty, brittle tex-ture is a good distin-guishing differs from most ^ „ „ ,. ,, „ J. ,1 ,^ 111 J?IQ- 9-—Ustuhna zonata ; section of fructification. of the other black, x6. brittle, encrusting fungi which are encountered on a Kubber estate, in that itis only attached to the substratum at one point, or whenseveral fructifications have fused together, at a few scatteredpoints. Consequently it can readily be detached whole fromthe bark. On the other hand, most of the other fungi whichform black crusts are attached over their whole under-surfaceand cannot be lifted off. TJstulina zonata produces two kinds of spores. The
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