380 MANIPULATION. 



of the cells, and also by reason of the great contrast between 

 the colour of the cell wall and that o£ the granules. The 

 circulation also will be frequently found to vary in its direction 

 in two cells lying side by side, which is another material point in 

 which it differs from all the tribe either of Chara or Nitella. 



Best Method of Viewing the Circulation, — For this purpose, 

 in the summer months, when the plant is in its most vigorous 

 state, any one of the leaves may be taken, and after having 

 been cut in the manner previously described, laid upon a 

 slide with water, and covered with a piece of thin glass, or 

 placed in an animalcule cage, the chances are that it will 

 exhibit the circulation; if not, a little heat applied to it, either 

 by adding some warm water, or by placing the slide for a few 

 seconds over an argand lamp, will often start it off. In the 

 winter, the leaves that are turned a little yellow, or even those 

 which appear dead, will often show it the best ; these should 

 be cut some little time before they are wanted, and placed 

 in warm water immediately, or what has often succeeded 

 with the author is to place them in a small bottle with water, 

 and carry this in one of the pockets of the dress in which there 

 is the greatest amount of heat. Whenever the leaf has been 

 cut, the circulation will be deadened for a time ; but heat 

 applied in one of the ways above directed, will generally be 

 the means of restoring it to its former state of activity. 



Method of Cultivating Chara, Vallisneria, §-c. — Mr. Varley, 

 who has had great experience in these matters, addressed, in 

 1840, a letter to the editor of the Microscopical Journal on 

 the subject, and, as no better description than this can be 

 given, the author has thought proper to transcribe it nearly 

 verbatim : — 



" In cultivating these plants," says Mr. Varley, " it is only 

 requisite to take notice of the circumstances under which 

 Chara naturally thrives, and to imitate them as nearly as 

 practicable. 



" Firstly. The Chara tribe is most abundant in still waters 

 or ponds that never become quite dry ; if found in runnino- 

 water, it is mostly met with out of the current, in holes or 

 side bays, where the stream has little effect, and never on any 



