374 



MANIPULATION. 



a stem, with its whorls, is seen of the natural size in fig. 243, 

 and magnified in fig. 244 ; from the centre of each whorl a 



Fig. 243. 



Fig. 244. 



smaller branch is given off, and wherever this takes place some 

 very delicate filaments, called roots, are found to grow from 

 the opposite side. The main tube, as shown in fig. 244, is 

 covered throughout its entire length with eighteen smaller 

 tubes, and is coated very thickly in some parts with carbonate 

 of lime, which renders the stem both opaque and very brittle. 

 Belonging to the same family as the Chara is a genus termed 

 Nitella, in which there are several species that exhibit the 

 circulation, amongst them may be named the N. hyalina and 

 flexilis ; the stem of these plants consists of a single transpa- 

 rent glassy tube of a delicate green colour, with transverse 

 joints. In these the circulation can be viewed without any 

 preparation, but in the Chara vulgaris the stem will -often 

 require to be freed from its carbonate of lime before any trace 

 of it will be visible. A portion of the stem of Nitella flexilis 

 is shown of its natural size by fig. 245 ; when this is compared 

 with the Chara vulgaris the difference is manifest, as the joints 

 are not only more delicate, but there is no outer coating of 



