. Lessons in botany. Botany. Fig. 6g. Root of the common vetch showing root tubercles, Nitrogen gatherers. 163. How clovers, peas, and other legumes gather ni- trogen.—It has long been known that clover plants, peas, beans, and many other leguminous plants are often able to thrive in soil where the cereals do but poorly. Soil poor in nitro- genous plant food becomes richer in this substance where clovers, peas, etc., are grown, and they are often planted for the purpose of enriching the soil. Leguminous plants, especially in poor soil, are almost certain to have enlargements, in the form of no
. Lessons in botany. Botany. Fig. 6g. Root of the common vetch showing root tubercles, Nitrogen gatherers. 163. How clovers, peas, and other legumes gather ni- trogen.—It has long been known that clover plants, peas, beans, and many other leguminous plants are often able to thrive in soil where the cereals do but poorly. Soil poor in nitro- genous plant food becomes richer in this substance where clovers, peas, etc., are grown, and they are often planted for the purpose of enriching the soil. Leguminous plants, especially in poor soil, are almost certain to have enlargements, in the form of nodules, or '' root tubercles.'' A root of the common vetch with some of these root tubercles is shown in fig. 69. 163a. A fungal or bacterial organism in these root tubercles.—If we cut one of these root tubercles open, and mount a small portion of the interior in water for examination with the microscope, we shall find small rod-shaped bodies, some of which resemble bacteria, while others are more or less forked into forms like the letter Y, as shown in fig. 70. These bodies are rich in nitrogenous substances, or proteids. They are portions of a minute organ- ism, of a fungous or bacterial nature, which attacks the roots of leguminous plants and causes these nodular outgrowths. The organism (Phytomyxa leguminosarum) exists in the soil and is widely distributed where legumes grow. 164. How the organism gets into the roots of the legumes. —This minute organism in the soil makes its way through the wall of a root hair near the end. It then grows down the interior of the root hair in the form of a thread. When it reaches the cell walls it makes' a minute perforation, through which it grows to enter the adjacent cell, when it enlarges again. In this way it passes from the root hair to the cells of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not
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