CONJUGATED. 133 



through the membrane which invests them, escape through 

 the open extremity of the communicating tubes. 



When in a young condition, and before reproduction takes 

 place, the ConjugatecB are of a bright, beautiful, and shining 

 green colour, are highly lubricous to the touch, and the in- 

 dividual filaments are never entangled together, but placed 

 somewhat jjarallcl. As soon, however, as a union of the 

 filaments has occurred, these characters are for the most part 

 lost. The rich green colour fades to a yellow tint ; the fila- 

 ments no longer ghsten when removed from the water, or 

 feel slippery, but almost harsh and crisp under the fingers ; 

 they are now likewise much curled and twisted. The change 

 of colour is the result of diminished vitality, and the loss of 

 lubricity arises from the extension, amounting almost to ob- 

 literation of the sheath. 



The Conjugateco, Avith a single exception, dwell in Avaters 

 that are perfectly still, such as ponds, reservoirs, ditches, 

 pools, and extended marshes ; they are also, with a single 

 exception, unattached, roots not being necessary to them, for, 

 imlike the greater part of the Algm which have hitherto been 

 considered, and which are all provided with rootlilce organs, 

 they incur no risk of being swept away by the force of the 

 river, stream, or cascade in Avhich they delight to dwell. 

 The union between the filaments which is to occur, renders 

 a locality of the above description an essential to the very 

 existence of this family of plants, for without absolute 

 quietude of the water this conjugation would be frustrated. 

 In the only attached species Avith which I am acquainted, 

 and Avhich dwells in floAving water, I have never detected 

 conjugation of the threads. 



The ConjugatecB adhere strongly to paper, preserving their 

 shining appearance, but never their brilliant colours ; these 

 generally becoming almost black in drying. 



The quantity of air or gas eliminated by the Conferva^ 

 but principally by the Conjygatecp., in Avarm sunny Avcathcr 

 is very considerable. It is by means of the globules of air 

 given out by these plants in respiration, that such large 

 masses as are seen in the spring and summer montlis, covering 

 almost every pond and ditch, are sustained upon the surface, 

 K 3 



