418 M. Miiller on Substances inclosed in Mochastones, 



tiu-al, 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 

 figm-ed what I did see at b. 



It is a veiy 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 o-s^ii property. 



I was besides obliged to make my obsen^ations 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 tiiie Confej'vacea, 

 as Conferva, Zygnema, &c. 



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

 to di-aw attention to the fact, in the hope that later inquiries, should 

 I be so fortunate as to meet again with similar objects, may thi'ow 

 more light upon the matter. Found in Scotland. 



5. Plate X./^. 2, a. — INIass lobed, glaucous green, compressed. 

 A remarkalDle formation, resembling altogether a compressed 



dried Nostoc, w^hich it resembles also in colour. Indeed I know 

 not with what else to compare it. 



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

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

 equal thickness ; then* 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 monilitbmi sporidia which 

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

 ha\dng been separated fi'om one another by enonnous pressm-e. 



Tlie great distinctness of the frond seems to bespeak its affinity 

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

 &c., imder such pressure would scarcely have presened 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 fi'ond imder small mag- 

 nifj^ng powers appear some darker specks. If these are followed 



