70 Miscellaneous, 



indicates exactly the proportions which we find in <S. aquoreus, for 

 no S. Ophidion can become so large or thick, or have any such snout. 

 This may appear but a trifle, and in one respect it is so ; but on the 

 other hand, it is of very great importance for the clearing up of the 

 synonomy and all the errors which have thence originated. You 

 will oblige me by correcting this as soon as possible." — J. B. Fries. 

 Stockholm, 21st August. 



Note by Prof. Wiegmann. 

 *' At the same time that I fulfil the wish of my respected corre- 

 spondent, I must state that I certainly did not compare Bloch's 

 figure, whose work I had not at hand, erroneously supposing that 

 the only s[)ecimen in his collection had also been figured by him. 

 Hence it seems that Bloch did not distinguish both species." 



ON THE INFLUENCE OF NATIVE MAGNESIA ON THE GERMINATION, 

 VEGETATION, AND FRUCTIFICATION OF VEGETABLES. BY ANGELO 

 ABBENE. 



Among the various causes which produce barrenness in lands, has 

 been enumerated the presence of magnesia, because it had been ob- 

 served that the various magnesian soils are sterile. This opinion 

 has begun to lose credit, since Bergmann, who examined the compo- 

 sition of fertile soils, considered magnesia as forming one of their 

 principal constituents. 



Prof. Giobert has performed a number of experiments to inquire 

 into the action of native magnesia, which is found in numerous cul- 

 tivated soils. In the environs of Castellamonte and of Baldissero, this 

 substance is abundantly diffused in the soils cultivated with great 

 success, and which exhibit a vigorous vegetation. There are many di- 

 stricts in Piedmont and elsewhere, where the hi- carbonate of lime and 

 of magnesia is abundant in the cultivated lands, which produce beau- 

 tiful plants. Giobert concluded from these experiments ; 1st, that 

 native carbonated magnesia is not injurious to the various functions 

 of vegetables ; 2nd, that on account of the solubility of magnesia in 

 an excess of carbonic acid this earth can exercise an action analogous 

 to that of lime ; 3rd, that a magnesian soil may become fertile when 

 the necessary manure is employed. 



From these facts naturally proceeds the conclusion, that if the 

 magnesia was dissolved in an excess of carbonic acid and water, and 

 had entered like the lime into the composition of the sap, it ought 

 to be found in the plants with the potash, lime, oxide of iron, &c. 

 M. Abbene has ascertained this by the analysis of the ashes of 

 plants which had grown in magnesiferous mixtures. Moreover, he 

 endeavoured to find, by comparative experiments, whether the in- 



