52 Transactions of the 



absurd not to give this beautiful new species a name, and it is P. 

 cseruhus, Mihi ; but the body is investigated by an entomologist 

 with an anatomical bias, and he makes some important observations 

 deserving to be published, and the subject must have a name, so it 

 becomes P. iniesiinalis, Mihi; and to terminate an illustration 

 which might be carried to any extent, the caterpillar is found in a 

 field of carrots, a discovery so important must be published at once, 

 and it is P. Carotm, Mihi. The absurdity of such proceedings is 

 apparent from such an illustration as this, but in fossil botany the 

 terrible reality has to be encountered, and not only roots, stems, 

 branches, leaves, and fruit get different names, but different states 

 of the same stem receive different generic and specific names. In 

 the progress of my descriptions I shall take occasion to point out 

 the origin of these accidental states which have received generic 

 positions, and give my reasons for eliminating many worthless 

 names from the science. And I shall further, in the present case, 

 avoid introducing a name which in my next communication I may 

 have good reason for placing as a synonym to a well-known and 

 well-described species. 



The axis of this Lepidodendron (PI. VII,, Figs. 3 a, 4 a) is 

 entirely composed of scalariform tissue, which in the transverse 

 section is seen to be irregularly arranged, with the long diameter of 

 the vessels having a radial direction. The ends of the vessels are 

 more or less circular or polyhedral, and they are tolerably uniform 

 in size throughout, except at the exterior, where they are very 

 much smaller. It is important to notice that this central vascular 

 axis is not invested at any part of its circumference by the cyhnder 

 of radiating scalariform tissue which I described in Lepidodendron 

 selaginoides, Sternb.* The boundary line of this axis is irregular. 

 The small scalariform vessels project, and form recesses in which 

 free bundles of vessels of similar size occur. The projections are 

 the leaf bundles to be given off somewhat higher up the stem. 

 They form as yet only ridges, gradually becoming more prominent, 

 until they are completely separated from the axis, and then they 

 appear as described, as free bundles in a deep furrow. Those 

 bundles are to be found throughout the transverse section of the 

 stem ; near the centre they are always cut right across, but as they 

 proceed towards the circumference of the stem, they are cut in a 

 more and more increasingly oblique direction. This is the result 

 of the course the bundles take, being at first almost erect and 

 parallel with the axis, but gradually taking a more outward course 

 until they reach the base of the leaves. They spring from the 

 outer margin of the central vascular axis, a long way below where 

 they pass off to the leaf. 



Prof. Wilhamson, in his recent investigations into the organiza- 



* ' Mon. Micr. Journ.,' 1869, PI. XXVII., Figs. 1 6 and 2 h. 



