SECT. ii. OSCILLATOR1JE. 213 



together with the jelly in which they are imbedded, wave 

 with the slightest motion of the water. Floating masses 

 grow on large ponds or lakes, which give the water a 

 green tint. 



The structure of the Oscillatorise is microscopic. They 

 are minute filiform plants closely allied to the Nbstocs ; 

 and consist of transparent colourless tubular filaments 

 containing colour cells of various forms, more or less 

 separated from each other, and visible through their 

 transparent tubes ; the colour is usually some shade of 

 green, yellowish, or purple. In the genus Rivularia these 

 tubular filaments have a globular transparent cell at the 

 base, and are closely packed into little balls, either form- 

 ing small groups, as in the Bivularia nitida, or singly 

 attached to stones and rocks. In Bivularia nitida, 

 the filaments radiate from a centre. Some Oscillatorise 

 form velvety cushion-like patches upon rocks, others are 

 attached in tuffcs as parasites to other sea weeds, while 

 many are arranged in free or attached stratified bundles. 

 Lingbya furnishes a beautiful specimen of the latter. 

 The filaments in the stratified group are usually much 

 twisted and interwoven, and some of them exhibit singu- 

 lar oscillating motions, as the Oscillatoria littoralis and 

 spiralis, Spirulina tenuissima and others; one end of 

 the filaments remains at rest, while the other extremity 

 is in constant vibration. With a microscope the move- 

 ment in some species is seen to be from side to side like 

 a pendulum, in others it is spiral or twisting, and when 

 a fragment of the plant is set free when vibrating the 

 movement is progressive. If a fragment be put into a 

 glass of water, its edge in a little time becomes fringed 

 with short filaments radiating from central points with 

 their tips outwards. They soon detach themselves from 

 the fragment by their oscillations, and as their vibrations 

 continue after they are free, they swim with a spiral 

 motion to the edge of the water, and even ascend the 



