CONJUGATE.E. 133 



through the membrane which invests them, escape through 

 the open extremity of the communicating tubes. 



AYhen in a young condition, and before reproduction takes 

 place, the ConjugatecE 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 parallel. 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 glisten 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 Conjugatece, with a single exception, dwell in waters 

 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, 

 milike the greater part of the Algce which have hitherto been 

 considered, and which are all provided with rootlike organs, 

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

 river, stream, or cascade in which 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 tliis conjugation would be frustrated. 

 In the only attached species with which I am acquainted, 

 and which dwells in flowing water, I have never detected 

 conjugation of the threads. 



The Conjugatece 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 ConfervcB, 

 but principally by the ConjugatecR, in warm sunny weather 

 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 months, covering 

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



K 3 



