266 Messrs. Frankland and Kolbe on the 



of the species approximatus, figured and described in plate 216, 

 vol. iii. of the Fossil Flora, and the cruciatus^ figured in plate 

 19 of Brongniart's Histoire des Vegetaux Fossiles, their root- 

 lets are arranged in regular quincuncial order. In the largest 

 Calamites that to my knowledge has been figured, namely, 

 that called Gigas, plate 27 in Brongniart's work before alluded 

 to, the ribs and furrows begin to appear very like those of 

 Sigillaria, and the joints show indistinctly. 1 he termination 

 of the root of a Calnmites is exactly of the same form as the 

 terminal point of a Stigmaria, both being club-shaped. 



I am not aware that up to the present time much, if any- 

 thing, is known of the structure of Calamites ; but if it should 

 resemble that of Sigillaria, it may tend to prove that Calamites 

 are but young Sigillaria. 



In our observations it must not however be lost sight of, 

 that no central axis or pith has to my knowledge yet been 

 discovered in the stem of the Calamites like that found in Si- 

 gillaria. Both plants are proved to have had similar hahitatSy 

 and therefore it is very probable that they might have had 

 rootlets resembling each other without being the same plant. 

 Still, however, as Sigillaria was so long considered a separate 

 plant from Stigmaria, it is unphilosophical to take no notice 

 of the analogies of what are now considered distinct genera. 

 Although it will not by any means be safe to affirm that Sigil- 

 laria and Calamites are the same plant from their analogies, 

 still it is conceived that sufficient evidence has been adduced 

 in this paper to prove that the latter as well as the former 

 plants have generally grown on the places where they are 

 now found, and that the reason why one is so much more fre* 

 quently found in an erect position than the other, arises from 

 the circumstance of the stem of the one being much stronger 

 than that of the other. A deposit of mud on the branches 

 and leaves of the slender stem of a Calamites might weigh it 

 down and prostrate it, whilst the stout trunk of the Sigillaria 

 would resist such action and continue erect. 



XLIV. Upon the Chemical Constitution of Metacetonic Acid, 

 and some other Bodies related to it. By E. Frankland, 

 Esq. and H. Kolbe, Ph.D.^ 



T^HE researches into the constitution of organic compounds 

 •*- certainly belong to the most interesting in chemistry. 

 But they are always attended with more or less danger, and 

 those who, leaving the safer road of experiment, plunge into 

 the depths of hypothesis, and build up theories apparently 

 * Communicated by the Chemical Society; having been read April 19, 

 1847. 



