80 Goppert on Fossil Plants, and on 



and that, in the case of a vertical section of the Pinus sylvestris, 

 which was soaked in silico-hydro-fluoric acid, the punctured ves- 

 sels were converted into silica. In those which are changed into 

 reguline metal we see this phenomena very distinctly if we con- 

 tinue the red heat for only half an hour. By a longer continued 

 action of this degree of heat, the arrangement of the metal is so al- 

 tered that the connection of the vessels and cellular tissue is some- 

 what broken ; and now, (I cannot suppress the remark, although 

 I do not draw any conclusion from it), there is a great resemblance 

 to those hair-like forms in which the above mentioned metals 

 sometimes occur in the native condition. The richer a plant is in 

 potash and cellular tissue, a condition which occurs in herbaceous 

 plants, the less do these experiments succeed. It is true, that 

 after the heating there appears in the form of the plant, the earth 

 or the metal which has been employed, but, on pouring water 

 over it, nearly every thing is dissolved, and only separate vessels 

 or cells remain behind ; as, for example, we remark, in the leaves 

 of the ferns. Although these experiments, which also promise 

 much advantage to vegetable physiology, are capable of being- 

 carried much farther, yet, when we apply their results, first of 

 all, to the process of petrifaction, we can already understand 

 why only trees and shrubs occur truly petrified and never herba- 

 ceous plants. Shrubs occur more rarely than trees, because, 

 thouo-h they contain less potash than herbaceous plants, yet 



distinct division into fibres. The series of metamorphoses of this structure 

 may be represented in the following manner : The separating walls of the 

 epidermal cells gradually become individually developed, by acquiring more 

 substance, and by predominatiag as net-work over the cellular intervals. 

 These intervals become more and more contracted by the increase of the 

 parietal substance, and the fibrous tissue then extends itself; at last there ap- 

 pear anastomoses between the thick parallel fibres, which, being separated, 

 exhibit a tendency to form a net, and further indicate their importance as 

 separating walls. The more exact description and classification of these struc- 

 tures will form the subject of future investigations. In the mean lime the 

 following chief forms may be enumerated, 1st, cellular membrane; 2d, plain 

 fibrous net with and ■\/ithout stomata ; 3d, spiral-curved fibrous net with and 

 without stomata; 4th, moderately stretched fibrous net, loose, dense; 5th, 

 long stretched fibrous net with square anastomoses ; Cth, independent long 

 fibres without concrescence, partly straight, partly curved ; 7th, long fibres 

 with partial concrescence, and their passage into stone coverings and stone 

 fruit. 



