. A handbook of cryptogamic botany. Cryptogams. CYANOPHYCEM only temporary duration ; when it disappears it leaves the membra- nous sheath open at the extremity. This is especially well seen in Calothrix (Ag.). The ordinary mode of multi- plication of the Rivulariacese is by means of hormogones, frag- ments of the green portion which become detached from the rest of the filament, escape from the gelatinous envelope, move about with a creeping motion, eventually come to rest, invest themselves with a gelatinous sheath, and develop into a new filament in which the differenti- ation of the basal
. A handbook of cryptogamic botany. Cryptogams. CYANOPHYCEM only temporary duration ; when it disappears it leaves the membra- nous sheath open at the extremity. This is especially well seen in Calothrix (Ag.). The ordinary mode of multi- plication of the Rivulariacese is by means of hormogones, frag- ments of the green portion which become detached from the rest of the filament, escape from the gelatinous envelope, move about with a creeping motion, eventually come to rest, invest themselves with a gelatinous sheath, and develop into a new filament in which the differenti- ation of the basal and apical extremities is soon manifested. The formation of hormogones is confined to the lower and central portions of the filament, and commences only after the disappearance of the terminal hyaline hair. They vary greatly in length, being composed of from two to fifty pseudocysts. When fully formed, they glide slowly out of the sheath, seyeral often attached to one another. At the period of detachment of the hormogones the whole fila- ment displays a slow movement ; otherwise it is quiescent, the power of motion which in the Oscillariacese belongs to the entire filament being in the Rivulariaceae restricted to the hormogones. Beck (Verhandl. Gesell. Wien, 1886, p. 47) describes a peculiar mode of formation of the hormogones in Gloeotrichia natans,. Fig. "i^i,.—Calothrix crusiacea 1 (After Bornet.). 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 perfectly resemble the original Bennett, Alfred W. (Alfred William), 1833-1902; Murray, George Robert Milne, 1858-. London, New York, Longmans, Green, and Co.
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