. Botany of the living plant. Botany. irrfXjUlar nutrition 205 spots as roots, and vascular tissue extends from tlie stele into tliem as they mature. But tlieir structure is different from tjiat of roots (Fig. 150). They consist chiefly of parenchyma, which when young is found to be tra\'erscd by thread-like bacterial masses, extending from cell to cell. _From these masses numerous minute bodies are derived, which crowd the cells of the tubercle, but do not destroy the protoplasts, while the nuclei of the cellsremainwell nourishedand of large size (Fig. 156, 2). In annual Leguminosae the
. Botany of the living plant. Botany. irrfXjUlar nutrition 205 spots as roots, and vascular tissue extends from tlie stele into tliem as they mature. But tlieir structure is different from tjiat of roots (Fig. 150). They consist chiefly of parenchyma, which when young is found to be tra\'erscd by thread-like bacterial masses, extending from cell to cell. _From these masses numerous minute bodies are derived, which crowd the cells of the tubercle, but do not destroy the protoplasts, while the nuclei of the cellsremainwell nourishedand of large size (Fig. 156, 2). In annual Leguminosae the greatest development of these bodies in the cells is reached about the time of flowering. But from this time onwards their numbers diminish. Most of them become dissolved, and the evidence indi- cates that their organic materials arc drafted off into the conducting system of the host. When the seeds of the Legu- minous plant are ripe the nodules have shrivelled, and relatively few of the small bodies remain. These are set free into the soil as the nodules rot. The bodies thus set free are rod-like and motile, and arc called Bacterium radicicola. These Bacteria have been cultivated apart from the plant, and it appears that in presence of proteid and sugar they are able to bring the free nitrogen of the air into combination. The infection of the roots lias been traced to the root-hairs, and doubtless the infec- tive germs are derived from the former '^"" '55- . A 1 â 1 Root of Vicia Faba, w-ith nii- tubercleS rotted m the sou. A bright spot merous root-tubercles. Reduced. , 1-1-1 1 ⢠(.\fter Strasburger.) appears close to the tip ot the root-hair. This is a small mass of that gelatinous state of Bacteria known as the zooglaea stage. It works its way through the cell-wall into the cell, and extends downwards as the thread-like body already noted (Fig. 156, 3). It traverses the cells of the cortex to the point outside the stele, where the tubercle arises. Cell-divisi
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
