98 REPOKT — 1876. 



Recent Researches into the Organization of some of the Plants of the Coal- 

 measures. By Professor W. C. Williamson, F.ll.tS. 



In bringing the subject before the Geological Section the author chiefly aimed 

 at demonstrating the structural identity of Calamites and Calamodendron and of 

 Lepidodetidron and Sigillaria. The stems of Calamites described in his first 

 memoir published in the 'Philosophical Transactions ' were very young ones, in which 

 the highly distinctive Oalamitean organization was well preserved, and in one of 

 which the vascular cylinder, composed of a ring of detached woody wedges, was 

 enclosed in a thin parenchymatous imdifferentiated bark. He now exhibited a series 

 of specimens, beginning with one less than ^^ inch in diameter, in which the vas- 

 cular cylinder was represented by little more than a circle of the canals, one of 

 which is located at the inner angle of each vascular wedge, and in which tjie bark 

 was thin imditierentiated parenchyma. From this starting point, the author passed 

 through a series of intermediate examples up to one in which a large pith was sur- 

 rounded by a cylinder of vessels having a circumference of 15 inches, and which in 

 turn was enclosed within a bark 2 inches in thickness. The outer portions of the 

 vascular cylinder had lost most of the special arrangements of its tissues so charac- 

 teristic of young stems, which were now modified into a mass of thin radiating vas- 

 cular wedges, separated by equally thin medullary rays, the condition being almost 

 identical at the nodes and at the internodes. T"he tark also is now differentiated 

 into two layers, an inner parenchyma and a thick outer prosenchyma, the cells of 

 the latter assuming the prismatic type. There is little or no doubt that externally 

 to this the living plant possessed at least a third layer of parenchyma not preserved 

 in the author's specimen. 



A series of sections was then exhibited, demonstrating the erroueousness of 

 Bronguiart's distinction between Lepidodendron and Siyillaria. The author had 

 previously pointed this out in the case of the Lcpidodei.dra chaiacteristic of the 

 lowermost Carboniferous rocks obtained from the Burntisland deposit. He now 

 showed that it was equally true of the common L. selayinoidcs of the Upper Coal- 

 measures, whilst L. hnrcouriii has only the structure long ago described by Brong- 

 niart, viz. an inner vascular cylinder not developed exogeuously. All the other 

 Lepidodendra referred to possess an outer exogenous cylinder such as Bronguiart 

 believed to be characteristic of Sitjillaria, and which exists in the Anahathra of 

 Witham and tlie Diploxijlon of Corda. The author thus concludes tliat the Lepi- 

 dodendron harcourtii represents the lowest degi-ee of development seen amongst the 

 Lepidodendra, as isigillaria exhibited the highest, whilst the Lepidudcndrcn selagi- 

 noides of the Middle Coal-measures occupies an intermediate position. 



On the Junction of Ghranite and Old Red Sandstone at Corrieand GlenSannox, 

 Arran. By E. A. WiJNscH, F.O.S. 



The object of this paper is to show by specimens and diagrams that the rock 

 intervening between the granite and the stratified rocks on the nortli-east coast of 

 Arran is not, as held by Professor Kanisay and Dr. Bryce, a band of slate. There 

 8 no slate in all Glen Sannox, nor as far south as Brodick Castle. The sedimentary 

 rocks, Old Red and Carboniferous, cropping upon the shore, retain in a remarkable 

 manner the same general dip, the initial direction of which is given to them by 

 the great anticlinal axis of mid Sanuox, and abut right against the granitic nucleus 

 of the island. 



As we approach the junction, at a height of about 800 feet from the sea-level, 

 the angle of inclination becomes more highly inclined, and the hitherto clearly 

 stratified beds assume a granitoid structure. 



At the point of cont,act the Old Red iSaudstone is so altered as to resemble slate, 

 and was mistaken for such and circumstantially mapped down as an extensive 

 band of slate by Dr. Bryce ; but no one can mistake the real character of the rock 

 if he begin his examination in the bed of the burn, about 60 yards below the 

 junction, where the Old Red Sandstone is seen exposed in its unaltered state, fine- 



