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cavities. I regret that the author has not explained this sub- 

 ject more accurately and elucidated it by drawings, as at 

 present I have no fresh Riccice at hand ; it appears to me 

 however as if these veins consisted only of elongated paren- 

 chymatous cells, and as such form the sides of the air-cavities 

 which gleam through the upper cellular layer. In Corsinia 

 he however observes, that there exists a large bundle of such 

 fibrous cells situated close together, only here and there tra- 

 versed by elongated almost prosenchymatous cells, and send- 

 ing out true ramifications, likewise consisting of several series 

 of cells. 



The occurrence of such veins in the Riccia would be highly 

 remarkable, as the Marchantice evidently stand much higher 

 and yet exhibit no such veins ; in the latter, their place is oc- 

 cupied by bundles of beautiful fibrils, which run exteriorly, 

 surrounded only by ridged elevations. 



M. Nees von Esenbeck had the kindness to forward to me 

 a specimen of Corsinia for examination ; it was dry, but it ap- 

 peared to me to show plainly that those bundles of brown 

 fibrous cells belong no more to the Corsinice than to other 

 Riccice. I found however on one specimen, between the de- 

 licate fibrils, a brown fibre, which agrees with the description 

 of the fibrous cells given by M. Lindenberg ; but I can af- 

 firm that this fibre, which also presented ramifications, did 

 not belong to the Corsinia. However, only the examination 

 of fresh specimens can decide this point. 



The RiccicB are otherwise so nearly allied to the Marchantice 

 in the appearance of their organs of fructification that they 

 can hardly be considered as a distinct natural family. 



Dr. Schleiden* has published a monograph of the genus 

 Ceratophyllum, containing much that is new, notwithstanding 

 all that has already been written on this subject. It is clearly 

 shown that Ceratophyllum must be separated from the Naiades 

 and reckoned among the Dicotyledons. The embryo has two 

 large fleshy cotyledons and a highly developed plumula ; it is 

 inclosed in albumen, and consists of a circle of leaves, which 

 at times is separated by an apparent internode from the cotyle- 

 dons, of a whorl of six undivided leaves, and lastly of two to 

 three whorls of forked leaves. M. Schleiden observed the em- 

 bryo sac in the axis of the nucleus long before impregnation, 

 Beitrage zur Kenntniss der Ceratophylleen. Linnaea, xi. p. 513. 



