386 Prof. Meyen's Report of the Progress of 



larice, although in this case the separation does not take place 

 at the point of the sporangia, which however, as will be im- 

 mediately shown, occurs also in Confervas. From various phte- 

 nomena it seemed probable to Mohl that in the several species 

 also of the genus Spirogyra, Link, (Zygnema, Ag.), the single 

 cells possess the property of dividing themselves in their centre 

 by a septum. This supposition I can fully confirm ; for 

 experiments made on Spirogyra when budding (which since 

 Vaucher's* observations it appears no one hail repeated,) 

 have shown it in a most evident manner. At the commence- 

 ment in this case it is always the last member remaining in 

 the burst capsule, which increases considerably in length, and 

 divides itself by a new septum into two cells, upon which the 

 inferior cell lengthens, &c. Soon after some of these new 

 cells lengthen and divide again. 



These data, viz. the increase of the cells in microscopical 

 plants by separation, are of great importance, and have hitherto 

 been but rarely mentioned, and never with so much certainty. 

 Carusf formerly observed how the ends in Achyla protifera 

 Nees, separated by an apparent cellular septum from the 

 other parts of the sac; Carus in the same memoir has also 

 mentioned several observations on thegradual contraction down 

 to the complete separation. The origin of the fruit of the 

 Vancheria by constriction was also known ; hitherto however 

 no general conclusions on the growth of these plants by sim- 

 ple separation of the cells had been mentioned till Dumortier 

 discovered a similar increase at the terminal cells of Con- 

 ferva aurea%. As soon as the terminal cell of this Conferva 

 had become considerably longer than the preceding members, 

 a septum formed in its interior; this observation is quite 

 similar to that of Mohl on Conferva glomerata. A similar mode 

 of increase, viz. that by forming septa, was also observed by 

 Morren § in the Closterice, which this accurate naturalist is 

 completely justified, by his very convincing reasons, in classing 

 amongst vegetables, on which subject however we shall by 

 and by have more to say. 



It would now be of the greatest importance, if the datum, 

 first confirmed by Dumortier, that cells can increase by a 

 formation of septa, could also be demonstrated in the more per- 

 fect plants; this has been accomplished with tolerable certainty 



* Hist, des Conferves. PI. 4, 5 et 6. 

 t Nova Act. Acad. C. Nat. Cur., t. xi. p. 503. 



X Recherches sur la Structure comparee et le Developpement des Anhnaux 

 ctdes Vegitaux. Bruxelles, 1832, p. 10. 



§ Sur les Closth'ies, Ann. des Scienc. Nat., vol. i. p. 274. 



