28 



CHARACEiE. 



[Algals. 



brown by iodine and not dissolved by ammonia as animalcules are. (Ann. Sc. N. 2 ser. 

 14, 65.) They are probably analogous to the elastic spii-es of Equisetum. 



There are two other points deservuig of attention in Charas ; 1st, the calcareous 

 mci-ustation of some species ; and 2dly, the visible and rapid motion of the sap in the 

 articulation of the stem. 



Of the genera, Nitella is transparent and free from all foreign matter ; but Chara 

 contams, on the outside of its central tube, a thick layer of calcareous matter, which 

 renders it opaque. This incrustation appears, from the observations of Greville (FL 

 Edin. 281), not to be a deposit upon the outside, and of an adventitious natm-e, but a 

 result of some peculiar economy in the plant itself ; and according to Brewster, it is 

 analogous to the siliceous deposit in Equisetum, exhibiting similar phenomena. 



Whatever is known of the motions of the fluids of vegetables has been necessarily a 

 matter of inference, rather than the result of direct observation ; for who could ever 

 actually see the sap of plants move in the vessels destmed 

 to its conveyance ? It is true that it was known to botanists 

 that a certain Abbe Corti, of Lucca, had, in 1774, published 

 some remarkable observations upon the circulation of fluid 

 in some aqviatic plants, and that the accuracy of this state- 

 ment had been confirmed by Treviranus so long ago as 

 1817 ; but the fact does not seem to have attracted general 

 attention until the publication, by Amici, the celebrated 

 professor at Modena, of a memoir in the 1 8th volume of 

 the Transactions of the Italian Society, which was succeeded 

 by another in the 19th. From all these observers it appears, 

 that if the stems of any transparent species of Chara, or 

 of any opaque one, the incrustation of which is removed, 

 are examined with a good microscope, a distinct cm'rent 

 will be seen to take place in every tube of which the plant 

 is composed, setting from the base to the apex of the tubes, 

 and returning at the rate, in Chara vulgaris, of about two 

 lines per minute (v. Ann. des Sc. 2. 51. line 9) ; and accord- 

 ing to Treviranus this play is at any time destroyed by the 

 application of a few di'ops of spirit, by pressure, or by any 

 laceration of the tube. Such is the nature of the singular 

 phenomena that are to be seen in Chai'as. Those who 

 are anxious to become acquainted with the details of 

 Amici's observations will find his first paper translated in 

 the Annales de Chimie, 13. 384, and his second in the 

 Ann. des Sc. 2. 41 ; that of TrcsTi'anus is to be foimd in 

 the latter work, 10. 22. The observations made upon 

 Chara circulation by the foregoing authors have been much extended by the careful 

 inquiries of Solly, Slack, and Varley, whose remarks are to be found in the Trans- 

 actions of the Society of Arts, vol. 49, p. 177, and vol. 50, p. 171 ; and by Donnd, 

 Dutrochet, and others, m the Ann. Sc. Nat. 2 ser. vol. ^,pp. 5, Qo, 80, and 10, p. 346. 

 As however they relate to physiological and not to systematical questions I forbear to 

 dwell upon them in this place. 



The creation of plants of this order would appear to have been of a very recent date, 

 compared with that of Ferns and Palms, or even Algals, if we are to judge by their 

 fossil remams, called Gyrogonites, which are found for the first time m the lower fresh- 

 water formation, along with numerous Dicotyledonous plants resembling those of our 

 own oera. In the recent Flora of the world they make theii* appearance everywhere 

 in stagnant waters, in Europe, Asia, and Africa, in North and South America, in New 

 Holland, and in either India. They are most common m temperate coimtries. 



We can scarcely claim any knowledge of their uses. Theu' stems, often encrusted 

 with lime in the state of carbonate according to some, and of the phosphate according 

 to others, are probably useful as a manure. The fetid effluvium arising from them is 

 regarded as very unhealthy, and one of the sources of the malaria of the Campagna of 

 Rome. 



GENERA. 

 Chara, L. Nitella, Ag. Charopsis, Kiitz. 



Numbers. Gen. 3. Sp. 35. 



Fhcviales. 

 Position. — Ceramiacea?. Charace^. . 



XII.* 



Equisetaccce. 



Fig. Xil.*— A magnified vieM- of Nitella, with the motion of its sap sliown by arrows. 



