82 



diffused light. The agitation has changed, as it would ap- 

 pear, the regular order of the molecules of the liquid, and 

 their aggregation has become confused. In this last state 

 they enjoy a mobility of which they were deprived in their 

 state of regular position ; and it is to be remarked that water 

 so changed with a mineral substance in solution and agitated, 

 has more molecular mobility, and is more susceptible of cir- 

 culation than was the pure water before this solution." 



With the following extract, this epitome of Dutrocbet's 

 letter on the circulation of Chara may be concluded : 



" After having filled tubes with acidulated milky water 

 I have closed them with the lamp. This liquid being fit 

 for circulation, being unalterable, and not being able to lose 

 any thing by evaporation, it follows that being exposed to 

 the light it possesses the condition of a perpetual circulatory 

 movement, with nocturnal intermissions, and further, with a 

 winter intermission, which exists but when the temperature 

 is inferior to 5 R. One might say, metaphorically, that this 

 liquid is, during the night, in a state of sleep, and during 

 the day, in a state of wakefulness ; one might say also that 

 its repose in winter is a state of hibernation. It might be 

 supposed at first view that these phenomena bore some ana- 

 logy to the state of sleep and of wakefulness of plants, and 

 to their state of hibernation." 



An experiment in reference to the circulation of the Clia- 

 racece may here be referred to, viz. that the application of a 

 ligature to the centre of a cell does not destroy the circulation 

 therein. 



This experiment was originally made by Raspail. 



A general description having now been given of the 

 structure and circulation of Chara and Nitella, a few other 

 particulars still remain to be noticed. 



A delicate membrane lines the interior of each cell, 

 having little or no attachment to the one which constitutes 

 the proper cell membrane, and which is therefore easily 

 separable therefrom, save at the lateral colourless longitu- 

 dinal lines, which are formed probably by its attachment. 



