. Carnegie Institution of Washington publication. ROOT-NODULES OF LEGUMINOSAE. I05 Beyerinck found swarmers in minute nodules which were still inclosed in the mother root. He divides the root-nodule organisms into groups and varieties as follows: Group I.—This contains the larger more hyaline colonies. Growth absent or difficult on meat peptone gelatin. Growth is favored by cane-sugar or grape-sugar. vSwarmers are very minute. The bacteroids are two-armed, globose, or pear-shaped. Meristem is always present in the nodules. The primary bark of the nodule is closed. Slime threads are distinct. T
. Carnegie Institution of Washington publication. ROOT-NODULES OF LEGUMINOSAE. I05 Beyerinck found swarmers in minute nodules which were still inclosed in the mother root. He divides the root-nodule organisms into groups and varieties as follows: Group I.—This contains the larger more hyaline colonies. Growth absent or difficult on meat peptone gelatin. Growth is favored by cane-sugar or grape-sugar. vSwarmers are very minute. The bacteroids are two-armed, globose, or pear-shaped. Meristem is always present in the nodules. The primary bark of the nodule is closed. Slime threads are distinct. The following forms belong here: B. radicicola, , vicia-kirsutae, trijoliorum, pisi, lathyri. Group II.—Colonies more cloudy white. Growth better on meat peptone gelatin. Swarmers more rod-shaped, somewhat longer. Bacteroids like the bacteria, that is, seldom branched. Slime threads absent or little developed. Mostly no meristem in the nodules (Robinia an exception). Three types occur: (1) Phaseolus type; (2) B. radicicola, var. lupini; (3) Robinia type. In Yicia faba, as the bacteroids are exhausted the color of the cytoplasm changes from reddish to intense green. The bacilli from this plant when grown in Faba stem gelatin in a cool place (cellar) were alive and motile at the end of a year. Active cultures can be obtained from all parts of the nodules which have been exhausted by the bacteria. They are present in a living condition therein in great numbers. The result is quite different when the host empties out the contents of the bacteroids. Then it is more and more difficult to get any bacterial growth from the meristem. The longer the bacteria remain in the nodules the more bacteroids occur. Beyerinck found saprophytes in the nodule tissues mixed in with B. radicicola and named at least two—B. luleo albus and B. agglomerans. Another green fluorescent form thought certainly to come from the nodule was identified as B. fluoresceins putidus. A form resembling B
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