. A handbook of cryptogamic botany. Cryptogams. 442 PROTOPHYTA The blue-green colour of phycocyanin is sometimes replaced by a red or violet pigment. Scott finds a cell-nucleus in several species of Oscillaria. The only certainly known mode of multiplication of the Oscillariaceae is by a filament escaping from its mucilaginous sheath, and breaking up into hormogones, each composed of a small number of pseudocysts, which round themselves oif at both ends and develop into new filaments. The family derives its name from the oscillating or wavy motion with which the filaments are endowed. This con
. A handbook of cryptogamic botany. Cryptogams. 442 PROTOPHYTA The blue-green colour of phycocyanin is sometimes replaced by a red or violet pigment. Scott finds a cell-nucleus in several species of Oscillaria. The only certainly known mode of multiplication of the Oscillariaceae is by a filament escaping from its mucilaginous sheath, and breaking up into hormogones, each composed of a small number of pseudocysts, which round themselves oif at both ends and develop into new filaments. The family derives its name from the oscillating or wavy motion with which the filaments are endowed. This consists in a creeping movement in the direction of the length of the filament, now backwards and now forwards, accompanied by a curvature of the filament and rotation round its own axis ; but, according to Borzi, this power of motion is limited to the reproductive period. The filaments of the Oscillariacese have a remark- able power of resistance to both cold and desiccation, to which they are adapted by the encysting of the filament and hardening of the mucilaginous sheath. The movements of the Oscillariacese are greatly influenced by temperature and light, being much more active in warmth and sun- shine than in cold and shade, but their cause is involved in considerable obscurity. Cohn (Arch. mikr. Anat., 1867, p. 48) observed that the oscillating movements take place only when the filament is in contact with a solid substratum. Siebold (Zeitschr. wiss. Zcol., 1849, p. 284) states that if the water in which they grow is coloured by indigo, the particles collect round the filaments of Oscillaria up to their apex, whether they are in motion or not. Some- times creeping spiral lines of pigment begin to be formed at both ends of the filament and meet in the middle, where the particles become heaped up into little balls ; or sometimes this begins in the middle and advances to both ends. The mode in which the particles of indigo adhere to the filament and to one another appears to in
Size: 834px × 2996px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, bookpublisherlondonnewyorklongm
