the Process of Petrifaction. 79 



The potash skeleton, whicli may be distinctly seen in most 

 plants, * is dissolved, and I thought at first that I remarked 

 (and I so stated it hi the preface to my work on fossil ferns, p. 

 xix.) that only the vessels were filled or injected with metallic 

 or earthy mattei-, and that their sides were destroyed by the ac- 

 tion of the fire. When, however, I experimented in the same 

 way on several plants which contained less alkali, I saw, in com- 

 pany with my much respected friend Mr Purkinje, that, for ex- 

 ample, by immersing in an iron solution the wing-like appen- 

 dages of the seeds of the Pinus sylvestris, -f the walls of thei?- 

 peculiar Jihre-likejbrmed cells were actually converted into iron ; 



" The interesting memoir of Struve (de silicia in planlis nonnullis. Berol. 

 1835) treats of the siliceous skeleton of plants, and I had ample opportunity 

 of confirming his results. Several plants, as the Chara, yield a calcareous 

 skeleton. 



-j- Regarding the peculiar structure of the still little known membranes of 

 the seed-capsules, Professor Purkinje had, in the year 1832, instituted a series 

 of interesting investigations, of which I am induced to give here a more par- 

 ticular account, because the conclusions at which he has arrived have been only 

 published in a tract not intended for sale, and which has had but little circu- 

 lation, viz. in the " Uebersichl der arheiten und verhandlungen der schlesischeit 

 Geselhchaft fur vaterl. kullur im J. 1832 ;" p. 62 to 65. On the 29th November 

 1832 Professor Purkinje continued the microscopic investigations commenced 

 in the previous year, on the peculiar structure of the inner membrane of the 

 seed capsule, and for this purpose he employed a microscopic collection of 100 

 specimens, which he demonstrated by lamp light to the numerous members pre- 

 sent, and with the assistance of Ploss's large microscope. The continuous union 

 in most plants of this membrane with the epidennis by means of the style, 

 might be expected from the analogy, if not from the identit}', of the two 

 membranes ; (just as in the bodies of the higher animals the epidermis, en- 

 tering into the interior, stands in connection with the mucous and serous 

 membranes). This analogy was still more confirmed by numerous examples 

 which occur in different genera, viz. in the Liliacese, Eanunculacete, and 

 Solaneae, where the membrane is frequently perfectly similar to the epider- 

 mis, and where even, in the first two, distinct stomata are met with. But 

 this analogy seems somewhat doubtful when we notice that in most genera, 

 as in the Leguminosae, Siliquoste, E,osaceae, &c., the fibrous structure of this 

 membrane predominates so much that it would appear bold to find in it <in 

 analogy or identity with the epidermis, as its fibrous tissue would rather point 

 to a resemblance to the under bark. This contradiction disappears when we 

 examine whole ranges of forms, and understand the separate members in their 

 transitions, for then we find that the most opposite extremes can be reconciled. 

 The Liliacese are best suited to this kind of investigation, partly because in 

 them the inner capsular membrane is remarkably well developed, and partly 

 because they exhibit the perfect series from the cellular structure to the most 



