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 Oscillariacese 



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 off 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 Oscillariaceae 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.Zool., 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 indicate the excretion of mucilaginous protoplasm. 



Fig. 368 — Oscillaria t^nu s Ag. 

 ( X 400). (After Cooke.) 



