418 M. Miiller on Substances inclosed in Mochastones. 



tural, as such places, as said above, become black from the oil 

 used in polishing. Found at Oberstein. 



4. Plate X. fig. 1. — A Conferva in a green jasper [Prase]. 

 Threads simple, short, curved, containing spiral threads (?). b — d. 



I am obliged to place a note of doubt here, since I am not quite 

 sure whether what I saw was a spiral as in Zygnema : I have 

 figured what I did see at b. 



It is a very difficult task to examine objects like this. We can 

 examine only that portion which lies close to the surface, and it 

 is then always matter of chance whether one falls in with anything 

 of interest. I was unable to prepare thin sections, as the speci- 

 mens were not my own property. 



I was besides obliged to make my observations mostly by means 

 of concentrated lamp-light, in order to transmit more light through 

 the whole stone, and may therefore have been subject to some 

 optical deception. 



I could not ascertain the exact place in the system of Algae -to 

 which the Conferva belonged, being unable to ascertain its inner 

 structure. The thickness of the threads, which are distinct though 

 congregated, seems to place them in the series of true Confervacece, 

 as Conferva, Zygnema, &c. 



In conformity with the intention of these notes, I am content 

 to draw attention to the fact, in the hope that later inquiries, should 

 I be so fortunate as to meet again with similar objects, may throw 

 more light upon the matter. Found in Scotland. 



5. Plate X.j^. 2, a. — Mass lobed, glaucous green, compressed. 

 A remarkable formation, resembling altogether a compressed 



dried Nostoc, which it resembles also in colour. Indeed I know 

 not with what else to compare it. 



The vegetable has certainly once been a frons plicata, since we 

 find the single folds lying one over the other. They are not of 

 equal thickness ; their colour is also here and there darker, where 

 the layers of folds are darker. The outline is very delicate and 

 distinct. 



Under the microscope the whole appears like a compressed ma- 

 cerated mass. I could not perceive the moniliform sporidia which 

 are peculiar to the genus Nostoc, probably in consequence of their 

 having been separated from one another by enormous pressure. 



The great distinctness of the frond seems to bespeak its affinity 

 to Nostoc, as the lower Algee, Palmella, Coccochloris, Microloa, 

 &c, under such pressure would scarcely have preserved their out- 

 line, their mass being too gelatinous, while in most species of 

 Nostoc it is of a firmer consistence. From want of globules it is 

 impossible to name it. 



Fig. 2, b — g. — In certain portions of the frond under small mag- 

 nifying powers appear some darker specks. If these are followed 



