. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Cycads are actually causedby the endophytic Alga. He found that the Alga maintained its existence 3—2 36 Myxophycese in the soil, and that it entered the roots regularly at the beginning of everyautumn through the lenticels. Spratt (11) confirmed the fact that the Algaentered the roots through the lenticels, and showed that this was accomplishedby means of gonidia which were developed from heterocysts and sporespresent in the soil. There is n
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Cycads are actually causedby the endophytic Alga. He found that the Alga maintained its existence 3—2 36 Myxophycese in the soil, and that it entered the roots regularly at the beginning of everyautumn through the lenticels. Spratt (11) confirmed the fact that the Algaentered the roots through the lenticels, and showed that this was accomplishedby means of gonidia which were developed from heterocysts and sporespresent in the soil. There is no doubt in this case of the symbiotic relationshipbetween the Alga and the two nitrogen-fixing Bacteria, and there is everyprobability that the Cycads benefit to some extent by being able to absorbcertain products of the metabolic activity of the lower organisms. Needlessto say, both the above species of Anab&na are considerably different fromthe more normal species of the genus, and both have degenerated. An endophytic member of the Nostocacese also lives in the hollowleaf-auricles of the Hepatic Blasia, but its exact relationships with its. Fig. 22. Part of a transverse section of tubercle-like root of Ci/ciis showing the algal zone ()containing Anab&na Cycadearum Eeinke and certain Bacteria, c., cork; , outer cortex;, inner cortex, x 400 (modified from Spratt). peculiar environment have not yet been investigated. Another occursin the stems of Gunnera. Hugo Fischer (04) has described a symbiotic relationship betweencertain of the Oscillatoriaceae which carpet the ground (such as Phormidiumautumnale) and Azotobacter Chroococcum. The nitrogen-fixing activity ofthe Bacterium enables the Blue-green Alga to make use of atmosphericnitrogen. A still more remarka,ble member of the Nostocacete is Richelia intra-cellularis Johs. Schmidt, which lives within the cells of marine species ofRhizosolenia (fig. 23). As this Alga occurs within the living cells of
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