458 Intelligence and Miscellaneous Articles, 



1st. Influence of temperature. — The circulation exists at the freezing 

 point of water, but is slow. If the water in which the plant is placed 

 be gradually heated, the circulation is accelerated as the tempera- 

 ture increases ; at Qb° to QQ° Fahrenheit it becomes very rapid. It 

 then diminishes, and at 80° it is very much slackened. If the tem- 

 perature of 80° is continued the circulation after some time increases 

 in quickness and soon becomes very rapid. If the temperature be 

 then increased first to 94° and then to 104°, the same effect takes 

 place, that is, the circulation after a diminution in quickness is by 

 degrees accelerated; at 11 3° the circulation is stopped, and does not 

 return. 



It may be observed therefore that the plant which has been exposed 

 to a temperature below 113° first experiences a torpor, but that this 

 torpor disappears by degrees. Whenever the plant is submitted to 

 a sudden change of temperature of about 77° the rotary motion is 

 completely stopped, but begins again some time afterwards. In ge- 

 nerad a depression of temperature diminishes the quickness of the 

 circulation, while the elevation of temperature, provided it does not 

 exceed certain limits, augments it ; beyond that temperature a slack- 

 ening takes place. Cold produces the same phsenomena : it tends 

 to slacken the circulation, but the vital reaction restores to this cir- 

 culation a quickness which is far from attaining that which it ac- 

 quires under the influence of the action of increase of tempera- 

 ture. 



2nd. — Influence of Light. — Light only acts upon the circulation of 

 Chara in its quality of agent to determine its chemical actions of 

 nutrition and respiration ; but in regard to its action upon the exist- 

 ence, and upon the quickness of the circulation, it has no influence ; 

 the temperature being the same, there is no difference in the quick- 

 ness of the circulation either during the day or the night. 



3rd. Influence of mechanical irritation. — Compression by means 

 of ligatures has a primitive and direct effect, producing a suspension, 

 or simply a diminution of the motive action of the circulating fluid ; 

 but this action is soon re-established by the vital reaction. Incisions 

 produce the same effect : if the verticillated leaves are cut, situated 

 on the two opposite joints of a stem, the circulation in the central 

 tube is stopped, and does not begin again for some minutes. Punc- 

 tures produce also the same effects, provided they do not penetrate 

 into the cavity of the central tube ; in this case the circulation is en- 

 tirely stopped. 



4th. Influence of chemical agents. — A stem of Chara placed in 

 water containing one-thousandth part of its weight of caustic potash 

 or soda in solution stops the circulation after two or three minutes, 

 without return. With a solution containing but one two-thousandth 

 of alkali, the circulation at the expiration of five minutes becomes 

 extremely slow ; five minutes afterwards reaction begins, and the 

 movement becomes very rapid. After 25 minutes the circulation 

 again becomes very slow, and at the end of 35 minutes it entirely 

 ceases, without returning. Lime water destroys the circulation in 

 two or three minutes. A solution containing 50 parts of crystallized 



