M. Miiller on Substances inclosed in Mochastones. 419 



up gradually with liig-lier powers they appear as represented at 

 b — g ; they arc of the same colour as the frond and lie scattered 

 upon it, as if pressed to it. They are tender, scale-like mem- 

 branes (?) jagged at the border. 



It is sui-prising to find structm-es like these, which are the last 

 one should expect to find upon what, judging from habit, I have 

 considered as a Nostoc. 



Many no longer retain then* original orbicular form ; and more 

 are frequently torn into many divisions as at (e). 



If we inquire what this formation probably is, it is veiy pleasing 

 to be able to give a certain answer : they are forms which belong- 

 to the great family Desmidiacea amongst Algse, and indeed to the 

 genus Micrasterias. 



It has the greatest afiinity with Micrasterias lacerata, Kiitzing, 

 and I leave it for a while to the judgement of algologists. 



Since hitherto Micrasteria are known only as hydrophytes^ the 

 Nostoc must also be a water Alga. Found at Idar in the princi- 

 pality of Birkenfeldt. 



6. Fiff. 4 — 9. — More or less round, pinnate, moss-like fronds, 

 wiiih. a yellow-bro^^'n substratum, in the middle of which is gene- 

 rally a chcle ^^dth a dot in its centre. Under the microscope the 

 textm-e appears as in the foregoing, macerated, and we can there- 

 fore judge only fi'om habit what the production may be. 



If we examine first the cu'cle in its centre, vdih its own central 

 dot, it appears that this is the point to which the object was fast- 

 ened, and from whence as a centre the other branches proceeded. 

 It must have been gelatinous, more or less globose, as appears 

 from the gradually fading colom' and the very thin compressed 

 membrane ; it must have been conglobated, so as to receive its 

 present orbicidar form. The feather-like lines were branches, 

 whose branchlets were also gelatinous and conglobated. 



Tliis again then belongs to the family of Algse, being most 

 nearly allied to Chaetophora amongst the Nostochinece,^\io%Q frond, 

 as in Chat, endiviafolia, exhibits a similar branched structure. 

 Found in a clear chalcedony from Oberstein. 



7. Fig. 10. — Red organic masses, appearing to the naked eye as 

 small, more or less isolated dots, occurring in a clear chalcedony. 

 The circumjacent parts are yellow. This yellow field is bordered 

 by similar red dots, only larger and more distinct and tolerably 

 isolated. 



Under a weak magnifying power they appear like more or less 

 oval balls, generally very regular, sometimes much torn and 

 crushed, the one dark red, the other reddish yellow. 



As in fig. 2, a higher magnifying power sm-prises the inqui- 

 ring eye, when these dots, which still appear superficial and 

 isolated, are found to exhibit the forms represented in the 

 figm'es c — s. 



