122 



extracts; anfc 8fo$tract$ from dforticjn SfountaR 

 [From the Annales des Sciences NaturellesJ] 



C. Montague on the Nucleus of Sphterophoron. The apothecium of 

 this genus of Lichens is at first only an elliptical expansion of the ex- 

 tremity of a division of the plant. If, in this state, a longitudinal sec- 

 tion be made, the cavity will be found to be occupied by the nucleus, 

 which is of a diagonal form. This circumstance is owing to a hemis- 

 pherical projection of the medullary or central layer of the thallus, repre- 

 senting a kind of torus, from all parts of which, tubes, bearing sporidia 

 or thecse, diverge. The upper part of the sporangium is already filled 

 with this scobiform substance altogether different from the sporidia, 

 the colour of which is of a beautiful blue or transparent indigo, 

 but which appears very black when in a mass ; the thecae and spo- 

 ridia are tinted of a like shade, but for the most part paler. By 

 degrees the cavity enlarges, not only by the increase of the extremity of 

 the branch, but still more by the insensible depression of the internal 

 projection formed by the medullary layer of the thallus. 



The nucleus contained in the apothecium differs but little from that 

 of other Lichens. It is composed of straightened filaments, pressed one 

 against the other, exactly as in the proligerous plate of a Lecidea, and 

 united together by the intervention of a mucilaginous substance, a ready 

 absorbent of water. These tubular filaments, closed at their free extremi- 

 ties, have absolutely the form of asci or utricules of a Peziza. They are 

 linear, obtuse at the summit, and contracted into a short pedicel at their 

 base, which appears to be the continuation of the filaments of the me- 

 dullary layer. In their young state, they are perfectly transparent, and 

 contain an opaline moisture (humeur) in which appear hereafter trans- 

 parent globules. They are only to be seen by readjusting the focus of 

 the microscope. In a short time these filaments, which can only be 

 considered as true thecee, take on a bluish tint, becoming more intense 

 by age, preserve always the sky blue colour when viewed by transmit- 

 ted light. 



The sporidise become also more and more apparent in the thecse : whe- 

 ther globular or oblong, they are arranged in a single row. At length, 

 the theca is about to burst ; they remain free, and mix with the mass of 

 black dust, from which they are 'nevertheless distinct, and which is very 

 difficult, at least for Dr. Montagne, to determine the origin, for it exists 

 from the very first formation of the apothecium. 



The theca is from five to six hundredths of a millimetre in length, 

 by a two-hundredth in diameter. The sporidia, which are quite sphe- 

 rical, or rather longer than they are wide, acquire, when free, about the 

 yi^th of a millimetre in diameter. The sporidia are surrounded by a 

 transparent expansion (limbe) and are, like the thecae, of a blue colour. 

 March 1841,;?. 149. 



Agassiz on the Structure of the Scales of Fish. M. Mandl considers 

 that I am mistaken in affirming, that the scales are composed of super- 



