On a deposit of Fossil Diatomacese in Aberdeenshire. 93 



nucleus, stretching it and finally breaking through it (fig. 15 c). 

 I have found this condition regularly in all the ovules I have ex- 

 amined. The various organs only sketched out in slight out- 

 lines in figs. 12 and 13, are much more distinctly seen in such a 

 germ at this stage. We may here distinguish clearly two strongly 

 marked divisions, viz. 1, the germinal body ; 2, the first leaf. 



I have already used the term germinal body (Keimkorper) for 

 the part morphologically corresponding in the germinating Sela- 

 ginellm, for that, namely, out of which developes the terminal 

 bud of the stem and the root, which phsenomena I shall discuss 

 in the following section, since the immediately succeeding stages 

 of the embryo, while breaking through, do not essentially dififer 

 from this in form. 



[To be continued.] 



IX. — Notice of a deposit of Fossil Diatomacese in Aberdeenshire, 

 By George Dickie, M.D., Lecturer on Botany, King^s Col- 

 lege, Aberdeen*. 



It is unnecessary to insist here upon the very general occurrence 

 of silex in fresh and salt water, or the means by which it is dis- 

 solved and retained in solution ; the very general distribution of 

 Diatomaceous plants is a sufficient proof, if any such need be 

 brought forward. It may be, that by some process like that called 

 electrotype, the organisms in question are enabled to perpetuate 

 their own beautiful forms, the impressions being taken in the 

 purest transparent silex. The rapidity with which they are mul- 

 tiplied will account for the large deposits of fossil earth found in 

 difierent parts of the world, and the indestructible nature of the 

 mineral which they have the power of depositing in or upon their 

 tissue enables us to recognize them long subsequently to the 

 time when their vitality ceased. 



In the month of March last, two different substances were sent 

 to me for examination ; they were described as having been found 

 under a bed of clay at Premnay in the interior of Aberdeenshire. 

 One of them consisted of small solid fragments of a dull white, 

 the other had the form of a fine powder of a pure white. On ex- 

 amination it was found that the former consisted of decomposed 

 felspar forming a kind of porcelain earth, the other had no small 

 resemblance to some fossil earths with w^hose physical characters 

 I was not unacquainted ; accordingly, on submitting it to exami- 

 nation under the microscope, I found it to be entirely composed 



* Read before tbe Botanical Society of Edinburgh 8th June, 1848. 



