MICROSCOPIC WONDERS 17 



Things are not always what they seem, and many ardent 

 pond-hunters have thrown Nostoc back into the pond without 

 more than a cursory glance. A little lump of greenish-blue 

 jelly is all one finds. This minute lump of jelly, likened by 

 some to partially boiled tapioca, is the bulwarks of a colony of 

 Nostoc securely hidden in the centre. Under the microscope 

 the jelly is seen to be occupied by long chain-like objects, the 

 links of which are of various sizes and shapes. Some of the 

 chains are composed of small round cells, others of large square- 

 shaped cells. The former are the young Nostocs, the latter the 

 mature. The chains may increase in length, or else portions 

 of the threads break away and swim slowly until, finding a 

 suitable spot, they settle and secrete a gelatinous substance 

 that entirely covers them ; thus fresh colonies are formed. But 

 Nostoc has yet another method of propagating its species by 

 spores. 



One of the most fascinating micro-plants is Oscillatoria 

 tenuis not because its conduct is of great interest, but on 

 account of its peculiar manner of swinging to and fro like a 

 pendulum. This oscillation is most captivating, and the writer 

 has found it a most difficult matter to leave the microscope, 

 even at meal times, when Oscillatoria tenuis is under focus. 

 For this plant sways backwards and forwards untiringly, as if 

 there was nothing else to do but to swing itself to sleep. 



When the feeling prompts it, Oscillatoria tenuis swims very 

 slowly to a fresh situation, and there, anchoring, continues its 

 pendulum behaviour. Sometimes two or more of these plants 

 will remain close together, and then the effect is even more 

 surprising, for they interfere with each other's free movements, 

 and seem to push and struggle more like animals than plants. 



Perhaps the most popular aquatic plant is Spirogyra, one 

 of the most beautiful objects to be found abundantly every- 

 where. Its size makes it particularly easy to study, and the 

 vividly green spirals, so rich in colour, when properly lighted, 

 form a picture that once seen is not readily forgotten. At first 

 sight it is so typically an ordinary plant, that its subsequent 

 behaviour produces a feeling of great astonishment. One 

 examines it carefully, and comes to the conclusion that it is 

 a most beautiful filamentous weed. On placing some in the 

 live box, and examining it at intervals, the mycologist begins 

 to doubt his powers of observation, and wonders whether the 

 heat from the reflector is the cause of what he sees. For lo 

 and behold ! two pieces of the weed are seen to be approaching 

 each other, and then each begins to swell at a particular point, 

 forming lateral protuberances, which increase in size until that 



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