Botanical Society of Edinburgh. 153 



Actinocyclus are those described by Ehrenberg, and are new British 

 species. They exhibit the strong siliceous cellular tissue underneath 

 the moniliform structure of the surface. The examples of Triceratium 

 striolatum, and also Zyyoceros rhombus differed somewhat from the 

 figures and descriptions given of them, being provided with two spines 

 placed close to the projecting terminations or angles of the valve, and 

 which were always present in the examples that had come under ob- 

 servation. The surfaces of the valves were also seen to be dotted 

 over with small projecting nodules which gave them a very remark- 

 able appearance. These appearances may perhaps be attributable to 

 a more matured development of the siliceous structure. 



Among the remarkable forms found, although not considered to 

 belong to the Diatomacese, are the two varieties of Bacteriastrum, the 

 discs of which were three or four times the diameter of those described 

 by Mr. Shadbolt, from Port Natal, and the radiations more numerous. 

 Mr. Dallas directed attention to the structure of the Diatomaceae 

 as affording some of the most beautiful examples of geometric ar- 

 rangement of cells with which we are acquainted. There are only 

 three of the regular polygons which can be employed alone to fill up 

 the space about a point in a plane surface, namely the equilateral 

 triangle, the square, and the hexagon ; these forms and their angles 

 are accordingly found to prevail in the structure of the tissues. By 

 constructing the polygons it was shown that they arrange themselves 

 in straight lines, determined by the shorter axis of the figures, the 

 quadrilaterals having two directions in which the lines run, and the 

 hexagons three. 



2. "On the various sections of Coal, considered in their relation 

 to the Block, and the relative views of Histologists thereon," by 

 Mr. Neil Stewart. 



The author stated : — " Since last July, I have frequently been 

 employed in making drawings of sections of coal as seen under the 

 microscope by transmitted light. In the prosecution of this work, I 

 have felt great difficulty in bringing to my aid the willing zeal so 

 necessary to spirited delineation, and which can only be commanded 

 in proportion to the knowledge which the artist has of his subject. 

 This I can only account for by stating, that a suspicion passed upon 

 my mind from the beginning, that something was wrong with regard 

 to sections ; and this suspicion, which I frequently mentioned to gen- 

 tlemen engaged in the investigation of this subject, increased with 

 my knowledge, until on reading Mr. Quekett's paper in the ' Micro- 

 scopical Journal ' for January last, I found that he there expresses a 

 notion similar to mine, but immediately contradicts it by again return- 

 ing to the usually received opinion. With a view, therefore, to 

 satisfy my own doubts, and if possible to make a contribution to sci- 

 entific truth, I have examined cubical blocks of various coals by direct 

 light, and with my own hands have made sections from all the sides 

 of these, and again examined them by transmitted light. I have also 

 made drawings of such sections. 



" Professor Bennett expresses it as his opinion — and I believe he 

 holds it in common with others — that the red-coloured striae seen in 

 the longitudinal section of household coal are tubes or ducts — that 



